ELSEVIER The Science of the Total Environment 168 (1995) 33-56

Sorting and recycling of domestic waste. Review of occupational health problems and their possible causes

Otto M. Paulsen”“, Niels 0. Breuma, Niels Ebbeh@jb, Ase Marie Hansen”, Ulla I. Ivensa, Duco van Lelieveld”, Per Malmrosc, Leo Matthiasen’,

Birgitte H. Nielsena, Eva Mgller Nielsena, Bente Schibye”, Torsten Skov”, Eva I. Stenbaeka, Ken C. Wilkins”

‘National Institute of Occupational Health, Lers( Parka% 105, DK-2100 Copenhagen 0, Denmark bDepartment of Occupational Medicine, University Hospital of Copenhagen, Tagensvej 20,

DK-2200 Copenhagen K Denmark ‘Danish Working Environment Service, Landskronagade 33-35, DK-2100 Copenhagen 0, Denmark

Received 12 August 1994; accepted 21 October 1994

Abstract

In order to reduce the strain on the environment from the deposition of waste in landfills and combustion at incineration plants, several governments throughout the industrialized world have planned greatly increased recycling of domestic waste by the turn of the millennium. To implement the plans, new waste recycling facilities are to be built and the number of workers involved in waste sorting and recycling will increase steadily during the next decade. Several studies have reinforced the hypothesis that exposure to airborne microorganisms and the toxic products thereof are important factors causing a multitude of health problems among workers at waste sorting and recycling plants. Workers at transfer stations, landfills and incineration plants may experience an increased risk of pulmonary disorders and gastrointestinal problems. High concentrations of total airborne dust, bacteria, faecal coliform bacteria and fungal spores have been reported. The concentrations are considered to be sufficiently high to cause adverse health effects. In addition, a high incidence of lower back injuries, probably due to heavy lifting during work, has been reported among workers at landfills and incineration plants. Workers involved in manual sorting of unseparated domestic waste, as well as workers at compost plants experience more or less frequent symptoms of organic dust toxic syndrome (ODTS) (cough, chest-tightness, dyspnoea, influenza-like symptoms such as chills, fever, muscle ache, joint pain, fatigue and headache), gastrointestinal problems such as nausea and diarrhoea, irritation of the skin, eye and

Abbrevrattons: C.I.,, , 95% confidence interval; FEV,, forced expiratory volume in 1 s; lod, limit of detection; ODTS, organic dust toxic syndrome - also denoted ‘toxic alveolitis , ’ ‘mill fever’ and ‘toxic fever’; OEL, occupational exposure limit; OR, odds ratio, i.e. the ratio between the odds in favour of having the disease in the exposed group and the odds in favour of having the disease in the non-exposed group; TLV, threshold limit value; VOCs, volatile organic compounds.

* Corresponding author.

0048-9697/95/$09.50 0 1995 Elsevier Science BV. All rights reserved. SSDI 0048-9697(95)04521-N

34 O.M. Paulsen et al. / The Science of the Total Environment 168 (1995) 33-56

mucous membranes of the nose and upper airways, etc. In addition cases of severe occupational pulmonary diseases (asthma, alveolitis, bronchitis) have been reported. Manual sorting of unseparated domestic waste may be associated with exposures to large quantities of airborne bacteria and endotoxin. Several work functions in compost plants can result in very high exposure to airborne fungal spores and thermophilic actinomycetes. At plants sorting separated domestic waste, e.g. the combustable fraction of waste composed of paper, cardboard and plastics, the workers may have an increased risk of gastrointestinal symptoms and irritation of the eyes and skin. At such plants the bioaerosol exposure levels are in general low, but at some work tasks, e.g. manual sorting and work near the balers, exposure levels may occasionally be high enough to be potentially harmful. Workers handling the source-sorted paper or cardboard fraction do not appear to have an elevated risk of occupational health problems related to bioaerosol exposure, and the bioaerosol exposure is generally low. To our knowledge no studies have yet been published on occupational health problems and exposures in relation to recycling of glass or metal tins, or in relation to the production of biogas from biodegradable domestic waste. Limited information exists on the risk and causal factors of the occupational health problems, and analytical epidemiological studies and surveillance programmes need to be undertaken to elucidate causal links between exposures and work-related health problems. These programs can provide data which can be used for administrative regulations and recommendations, e.g. establishment of occupatio- nal exposure limits (OELs), to prevent occupational health problems at existing waste recycling plants as well as the large number of plants to be built throughout the industrialized world in the near future. When establishing such OELs attention should be paid to a series of technical problems which have not yet attracted sufficient attention: average versus peak airborne exposure, total versus inhalable aerosol exposure, microbial viriability, viable versus total microorgamsms and static area air sampling versus personal air sampling. In addition, synergistic interactions between the different components of the bioaerosol exposure as well as individual susceptibility may be of importance when OELs for exposures at waste sorting and recycling plants are to be established.

Keywords: Domestic waste; Recycling; Cornposting; Occupational health problems; Occupational exposure limit

1. Introduction

The deposition and burning of domestic waste causes a profound strain on the environment, e.g. potential contamination of ground water re- sources, organic and inorganic pollution of nearby surface water and carbon dioxide release from incineration plants contributing to global heating. In addition, the available space for the establish- ment of new landfills is becoming more limited. In order to reduce the current environmental problems, several governments, particularly in the industrialized world, have made plans aiming at increased recycling of domestic waste during the next decade.

In the USA, the goal of the Environmental Protection Agency is a 25% reduction in the deposition of waste at landfills by the year 1995 and a 50% reduction by the year 2000. Thirty-eight states have in different ways initiated plans to increase waste recycling (Petkov, 1993).

In 1991, the European Community issued a directive calling for the protection of the environ-

ment by the use of cleaner technologies, by stimu- lated recycling and by optimizing the conditions under which waste is disposed of at landfills (Ridets direktiv 1991, Karlsson, 1992). In France, the Minister of the Environment in 1992 pro- posed that all traditional landfills be closed dur- ing the next 10 years and extensive use of waste recycling and other waste handling methods pos- ing less strain on the environment be imple- mented. This includes the establishment of 160 large waste recycling and treatment plants result- ing in N 10000 new jobs (Karlsson, 1992). A somewhat similar plan has been decided upon in Denmark aiming at a profound reduction in the deposition of domestic waste at landfills, and re- cycling of at least 50% of the domestic waste before the end of the decade. The Netherlands’ National Environmental Policy Plan emphasizes that dumping of waste at landfills should be re- duced from 55% of all waste in 1988 to 10% in the year 2000, and recycling should increase from 35% to 55% (Brasser, 1990). The aim of the UK

O.M. Poulsen et al. / The Science of the Total Environment 168 (1995) 33-56 35

Government regarding domestic waste is that by the year 2000 50% of the recyclable waste should be reused. This corresponds to N 25% of all domestic waste (Jones and Probert, 1992). In 1992 5% was recycled and w 90% was dumped at 14 000 landfills.

Recent calculations of recycling costs in the USA show that cornposting of the biodegradable fraction of domestic waste costs $50~80/tori whereas the cost to deposit waste is $30-150/tori (Petkov, 1993). However, in European countries such as the Netherlands (Dalmijn, 1987), France (Karlsson, 1992) and the UK (Jones and Probert, 1992) the cost of depositing domestic waste at landfills is considered to be lower than the cost of incineration or cornposting of the waste. Hence, it may be anticipated that the cost of waste han- dling in the future will increase. In addition, it is foreseen that very large investments will be needed at the regional level to fulfil the require- ments of the governmental plans, and the number of employees occupied with waste sorting and recycling is expected to increase rapidly during the years to come.

Several reports have indicated that waste sort- ing and recycling is associated with occupational health problems such as pulmonary diseases, gas- trointestinal symptoms, mucous membrane and skin problems and musculoskeletal disorders (Boutin and Moline, 1986; Malmros et al., 1990; 1991; 1992; Sigsgaard, 1992).

The current knowledge of health problems and their possible causes in relation to the collection of domestic waste was reviewed in a previous paper (Paulsen et al., 1994). The aim of the present paper is to review health problems and potentially dangerous environmental agents in re- lation to sorting and recycling of domestic waste. A further aim is to highlight research areas in which further knowledge is required.

2. General description of waste sorting and recycling

In the present review, source-separated waste means a defined but mixed fraction of domestic waste, e.g. a reusable fraction composed of paper,

cardboard and plastic materials. Source-sorted waste is a more pure fraction of domestic waste, e.g. the glass or news paper fraction.

Many waste recycling systems are based on the collection of source-separated or source-sorted waste, which is further sorted to produce raw materials for recycling. As indicated in Fig. 1, which outlines the flow of domestic waste through collection, sorting and recycling, the fractions may be glass, metal, plastic materials, paper and card- board and biodegradable materials. Fig. 1 does not include the various combinations of these fractions which may occur when source-separated waste is collected.

The degree of separation of the domestic waste received by plants will govern the choice of equip- ment and work routines. If the waste is com- pletely sorted a high degree of automation can be implemented making protection of the workers relatively simple. On the other hand, poorly sepa- rated waste may require either manual sorting at the plant or other work routines in which the workers have direct contact with the waste. The degree of separation will to a large extent depend on local activities. The efficiency of source sepa- ration of waste at the household level is strongly influenced by how motivated the households are for doing this. The motivation is dependent on the degree of initial as well as on-going informa- tion from the local authorities (Andersen et al., 1992) including to what extent enforcement is used (Everett and Peirce, 1993).

3. Occupational health problems and their possible causes

Cross-sectional studies on occupational expo- sures and/or health problems in the waste sort- ing and recycling industry have been carried out in the US (Mandsdorf et al., 1982), Great Britain (Crooks et al., 1987), Finland (Rahkonen and Ettala., 1987; Rahkonen, 1992) and Denmark (Malmros et al., 1991). These studies have indi- cated that workers in this industry have an excess risk of work-related health problems such as mus- culoskeletal problems, pulmonary diseases, or- ganic dust toxic syndrome (ODTS) symptoms

36 O.M. Poulsen et al. /The Science of the Total Environment 168 (1995) 33-56

I ’ conecElon:Unsaparatfldhowehofdgerbage I

A

Magnetic metal

4 Basic plant . mechanical sorting

h \1

Combustible q io- fraction degradable

I

1 Landfillfng or incineration I R p&i--+ [zyq

+ Glass

factories

R 7

Manual sorllng

t

Mechanical sorting

t

I (1) Conectfon: Paperlcaldboald (2) Wec(bn: Glass I

I (3) collection: Met& I 1 Machaniyl sorting ]

R

I

Mechanical sorting

(5) Collection: Biodegradable househdd gatbege

R = Residual fraction of waste l-5, Collection of source separated household garbage

Fig. 1. Collection, sorting and recycling of household garbage.

O.M. Poulsen et al. / The Science of the Total Environment 168 (1995) 33-56 37

(cough, chest-tightness, dyspnoea, influenza-like symptoms such as chills, fever, muscle ache, joint pain, fatigue and headache), gastrointestinal problems and irritation of the eye, skin and mu- cous membranes.

In the field of occupational medicine, chronic pulmonary diseases attract particular attention since they may lead to a life-long reduction in work capacity and quality of life of the affected workers. A Danish cross-sectional study was per- formed to establish the odds ratio (OR) for dif- ferent pulmonary diseases and symptoms among workers at waste sorting plants (n = 231, paper sorting plants (n = 33) and garden composting plants (n = 16) as compared with water supply workers (n = 119) serving as a reference popula- tion (Malmros et al., 1991; Sigsgaard et al., 1994). Workers at waste sorting plants had a signifi- cantly higher risk of chest tightness (OR = 5.43; C.I.,,, = 2.01;14.64) and ODTS (OR = 17.19; C.I.,S%, = 1.86;158.52) (Sigsgaard et al., 1994). The cross-sectional type of study has a tendency to underestimate the risk of work-related health problems due to the so-called healthy worker selection. Heederik (1990) stated that the healthy worker selection of non-malignant pulmonary dis- eases may be relatively strong, and it cannot be excluded that some workers with predisposition for allergy may leave their jobs due to the devel- opment of symptoms. This hypothesis could ex- plain why Malmros et al. (1991) found that the serum IgE concentration was significantly lower among the waste sorting workers and paper sort- ing workers as compared with the water supply workers, and Sigsgaard (1992) found that among the waste sorting and recycling workers and 253 cotton mill workers the proportion of atopic workers was negatively associated with the con- centration of airborne dust and endotoxin expo- sure. No longitudinal studies, including also the workers who have left the job, have yet been carried out to assess the risk of work-related health problems among waste sorting and recy- cling workers.

still unknown. However, as summarized in Table 1, similar pulmonary and gastrointestinal prob- lems occur in other industries (e.g. pig and poul- try farms, animal feed mills, cotton mills, etc.), and in these industries a relationship has been demonstrated between the health problems and high exposures to airborne dust containing mi- croorganisms (total viable bacteria, total viable Gram-negative bacteria, total viable fungi) and microbial agents (endotoxin).

No OELs (occupational exposure limits) exist for airborne microorganisms or microbial toxins such as endotoxin. Rylander et al. (19831 sug- gested, as a rough protective measure, that air- borne exposure to Gram-negative bacteria should be kept below lo3 cfu/m3 of air. In addition, Rylander (1987) suggested the following tentative OELs for endotoxin with respect to the develop- ment of different symptoms after exposure to cotton dust: fever, 500-1000 ng/m3; chest tight- ness, 300-500 ng/m3; overshift decrease in the l-s forced expiratory volume (FEV,), 100-200 rig/m’; bronchitis (inflammation), 20 “g/m’ (un- certain). Castellan et al. (1987) found that experi- mental exposure to endotoxin in cotton dust (4 h) in concentrations < 10 “g/m3 did not result in a significant decrease in FEV,, whereas all expo- sures with concentrations > 50 “g/m3 resulted in a significant decrease in this lung function parameter. Eduard et al. (1993) found that expo- sure to lo6 fungal spores/m3 of air in saw mills was related to respiratory symptoms, mucous membrane irritation and ODTS-like symptoms. In addition, chronic exposure to fungal spores at concentrations in the range 106-lo9 spores/m” has been proposed as a tentative OEL for the development of allergic alveolitis (Malmberg et al., 1988). Since development of occupational al- lergic asthma is highly dependent on the individ- ual susceptibility, it may not be possible to sug- gest tentative OELs for fungal spores in relation to this disease. The Danish OEL for annoying organic total dust is 3 mg/m” (Danish Working Environment Service, 1992).

The causality of the occupational health prob- Little data are available on exposure to noise lems among workers at waste recycling plants is for workers at recycling plants. However, in recy-

38 O.M. Podsen et al. /The Science of the Total Environment 168 (1995) 33-56

cling plants several sources of loud noise (sep- araters, balers, shredders) may pose problems (Peterson and Vikstriim, 1984; Petersen, 1988; Malmros et al., 1990), and noise levels > 90 dB(A) at waste recycling plants have been reported (Mansdorf et al., 1982).

In the following sections, data on exposures to bioaerosols and adverse health effects in relation to different work environments of waste sorting

and recycling workers are compared with the data presented in Table 1 and the tentative OELs mentioned above.

3.1. Refirse transfer stations, landjills and incineration plants

General description of technology. At modem landfills, various disposal technologies are in use, including stratification or gabled terrace

Table 1 Investigations linking airborne microbial exposure to health effects

Industry Number of perso&

Exposure (airborne concentrations)

Health effects (dose-response relationship)

Reference

Cotton mill 445 (253 + 156)

Cotton mill 882 (443 + 439)

Cotton mill 248

Cotton mill 720 (414 + 306)

Cotton mill

(controlled

108 sessions with 24-35 each

conditions)

Cotton mill 15 (13 sessions)

(controlled conditions)

Cotton mill 107 (23 sessions)

(controlled conditions)

Endotoxin: 33-325 rig/m’

Dust: 0.4-1.2 mg/m3

Endotoxin: 2-550 “g/m3

Dust: 0.2-2.5 mg/m3

Gram-negative bacteria: 0.103-lo5 cfu/m3 Dust: 0.3-2.0 mg/m3 Bacteria and dust correlated

Endotoxin: O-l.6 mg/g dust

Gram-negative bacteria: IO’- 4 X lo3 &t/m3 Total viable bacteria: 103-10s &t/m3 Fungi: lo’-10’ &r/m3 Dust: 0.3-15 mg/m2

Endotoxin: 6-779 ng/m3

Dust: 0.12-0.55 mg/m3

Endotoxin: 70-5600 “g/m3

Dust: 0.09-4.0 mg/m3

Endotoxin: 80-12060 ng/m3

Dust: 0.5-6.9 mg/m3

Endotoxin and dust correlated

Related to byss. prev., FEV,%, FVC%

Related to FEV,% Not related to byss. prev.

Related to FEV,, chr. branch. Related to byss. prev. and FEV,% (except in highest exposure group). No relation to pulmonary function or symptom variables

Related to byss. prev.

Related to byss. prev.

No relation to byss. prev.

Related to byss. prev.

Related to byss. prev.

Not related to byss. prev. Not related to byss. prev.

Related to FEV,% (group mean)

Not related to FEVt%

Related to FEV,%, byss. prev., blood neutrophils increase over shift

Not related to FEV,%

Related to FEV,%

Related to FEV,%

Sigsgaard et al. (1992)

Kennedy et al. (1987)

Haghnd et al. (1981)

Cinkotai et al. (1977)

Castelfan et al. (1987)

Rylander et al. (1987)

Haghnd and Rylander (1984)

O.M. Poulsen et al. / The Science ofthe Total Environment 168 (1995) 33-56 39

Table 1 (Continued)

Industry Number of person@

Exposure (airborne concentrations)

Health effects (dose-response relationship)

Reference

Pig farms

Pig farms

Dairy farms

Poultry slaughter houses

Pouhly farms

Animal feed mill

Saw mill

Saw mill

62

51

28

23

47

440 (315 + 12.5)

;;8 + 19)

473

Endotoxin: 31-340 ng/m3

Gram-negative bacteria: 103-IO5 &r/m3 Total bacteria: 103-3 x 106 Dust: 0.5-23.5 mg/m3

Endotoxin: 40-330 “g/m3

Endotoxin: 10-50000 ng/m3

Endotoxin: 20-1500 ng/m3 Dust: 0.4-15.3 mg/m3

Endotoxin: 130-1090 ng/m3 symptoms Endoxtoxin correlated to dust

Endotoxin: 0.2-470 “g/m3

Dust: 0.2-150 mg/m3

Viable moulds: 3 x lo3 cfu/m3 Total moulds: 10’ spores/m3 Dust: 0.3 mg/m3

Total moulds: lo6 spores/m3 (and IgG antibody level to mould spores)

Related to FEV,, FVC, acute respiratory symptoms Not related to chronic respiratory symptoms Related to acute symptoms Not related to lung function Related to acute symptoms Not related to lung function Not related to any variable

Related to FEVt%

Not related to allergic alveolitis and febrile reactions

No relation to lung function and respiratory symptoms

Related to FEV,% and respiratory

Related to FVC, FEV, , PEF

Related to lung function but not as strongly as endotoxin

Related to FEV, and MEFrs decrease during working week

Respiratory symptoms and other symptoms suggestive of mucous membrane irritation, allergic alveolitis, organic dust toxic syndrome

Heederik et al. (1991)

Donham et al. (1989)

Rask-Andersen et al. (1989)

Hagmar et al. (1990)

Thelin et al. (1984)

Smid et al. (1992)

Dahlqvist et al. (1992)

Eduard et al. (1993)

Lung function parameters FEV,, FEV,%, FVC, FVC%. MEF,,, PEF see abbreviations. Byss. prev., byssinosis prevalence (% of workers with symptoms of byssinosis); Chr. branch., chronic bronchitis. aNumber of persons: total number of persons involved in investigation (number of exposed persons + number of controls).

(Rahkonen and Ettala, 1987). At the landfills, a traffic controller directs the unloading of the waste and special equipment, e.g. compactors, is used for the final deposition and compacting of the waste. To reduce nuisance to the local community the waste is frequently (weekly or even daily) covered with earth.

A typical modem municipal waste incinerator is designed for heat recovery in the form of steam. An incineration plant is composed of three

main areas. The front-end system (the tipping hall) is composed of an unloading shed, a refuse pit, a loading crane and a vibrating feeder. The second main area is the thermal part of the system composed of a drying gate, combustion gate, gate movement, burnout gate and boiler section. The third main area is associated with the proper disposal of incinerator discharge, both solid and gaseous, as well as the distribution of the excess heat from combustion.

40 0-M. Poulsen et al. / The Science of the Total Environment 168 (1995) 33-56

He&z problems. Crook et al. (1991) undertook a questionnaire based cross-sectional study on workers (n = 134) at waste transfer stations, incineration plants and landfill sites compared with a reference group of workers (n = 114). Based on the prevalence figures the authors of the present review have calculated the following OR values indicating an increased risk of cough (OR = 2.1; C.I.,s, = 1.1;4.2) and phlegm pro- duction (OR = 2.3; C.I.95q; = 1.2;4.7) most days for > 3 months/year, frequent diarrhoea (OR = 16; C.I.,,, = 1.9;138.5) and frequent fevers and sweating (OR = 3.3; C.I.,,, = 0.6;15.9). At a large Swedish incinerator facility between 1920-1985 an excess of deaths due to lung cancer (SMR = 355; C.I.,,, = 162;675) and ischemic heart disease (SMR = 138; C.I.,,, = 95;193) was observed (Gustavsson, 1989).

Ettala et al. (1989) described back injuries due to lifting heavy items and incorrect working pos- tures. Several of the workers complained about cold and draught. However, only a few workers were studied at the five junk yards and a waste incineration plant in Finland.

Exposures. Table 2 summarizes data on bioaerosol exposure in refuse transfer stations, landfills and incineration plants.

Crooks et al. (1987) reported high total bacte- rial counts both at refuse transfer stations, land- fills and incineration plants (Table 2). Similar high concentrations of total airborne bacteria were reported at incineration plants by Duckett et al. (1980) and Mansdorf et al. (19821, whereas lower airborne bacteria exposure levels were measured at Finnish landfills and incineration plants (Rahkonen and Ettala., 1987; Rahkonen, 1992). High airborne exposure levels of fecal coli- form ranging up to lo4 cfu/m” have been re- ported (Crooks et al., 1987; Duckett et al., 1980; Lembke and Kinseley, 1985) and high airborne concentrations of fungal spores were measured by Crooks et al. (1987) at refuse transfer stations and incineration plants.

Even though some of the data listed in Table 2 may be regarded as worst case measurements, it seems justified that bioaerosol exposure to dust, bacteria and fungal spores may, at least occasion- ally, be harmful, i.e. total bacteria exposure levels

ranging from lo’-10’ cfu/m3 have been related to the prevalence of byssinosis among cotton mill workers (Cinkotal et al., 1977) and fungal spore exposure at lo6 cfu/m” were related to respira- tory symptoms and mucous membrane irritation among saw mill workers (Eduard et al., 1993). In support of the hypothesis that handling of waste at transfer stations, landfills and incineration plants may pose a potential health risk due to high exposures to microorganisms, Mansdorf et al. (1982) found up to 10’ viable microorganisms per gram unseparated domestic waste, and Gaube et al. (1986) found 1O8-109 viable bacteria and 106-lOa viable Gram-negative bacteria per gram of unseparated domestic waste (Table 3). In addi- tion, Gaube et al. (1986) reported that the hands and clothing of workers handling unsorted do- mestic waste were contaminated by streptococci, enterobacter, coliforms and other microorgan- isms. Rahkonen and Ettala (1987) found that the sampling of microorganisms on workers hands with contact plates did not indicate noteworthy contamination, i.e. total bacteria counts of 19 samples ranged from 2 to 240 cfu/plate.

Exposure to dust exceeding the Danish OEL for organic dust (3 mg/m3) was observed for several work processes (tipping hall, compactor floor and conveyer) at refuse transfer stations (Mozzon et al., 1987), and at incineration plants dust exposures exceeding the OEL were mea- sured at the shredders (Mansdorf et al., 1982; Duckett et al., 1980). Very high dust levels (113 mg/m”) were measured when emptying cinders at a Swedish incineration plant (Petersen and Vikstrom, 1984). Airborne levels of heavy metals were well below accepted OELs (Mozzon et al., 1987; Rahkonen and Ettala, 1987) but exposure to respirable quartz was reported at a level com- parable with the OEL (Mozzon et al., 1987).

Several reports describe measurements of emissions of volatile organic compounds (VOCs) from landfills in the context of their environmen- tal danger for nearby residential areas. The ma- jority of these studies involve mixed waste (domestic and industrial) and they focus on the measurement of dangerous compounds (chlo- rinated organic and aromatic compounds) (Pel- lizzari, 1982; Shafer et al., 1984; LaRegina et al.,

Table

2

Con

cent

ratio

ns

of b

ioae

roso

ls in

air

sam

ples

fro

m g

arba

ge

trans

fer

stat

ions

, la

ndfil

ls

and

incin

erat

ion

plan

ts

Type

of

plan

t

Tran

sfer

st

atio

n

Wor

kpla

ce

- .._

_ ~--~

-

--..

Sam

plin

g D

ust

Bact

eria

(c

fu/m

3)

Fung

i R

efer

ence

te

chni

quea

(m

g/m

3)

Tota

l G

ram

-neg

ativ

e Fe

cal

Ther

mop

hilic

(c

fu/m

3)

stre

ptoc

occi

ac

tinom

ycet

es

2 Ti

ppin

g ha

lls,

com

pact

ors,

A:

b,c

to

rs,

conv

eyor

s, e

tc.

lod-

106

lod-

2 x

lo5

lod-

104

lad-

10’

102-

3 x

106

Cro

ok e

t al.

(198

7)

102-

3 x

105

Cro

ok e

t al.

(198

7)

103-4

x

104

Rah

kone

n et

al

. (19

87)

5 x

102-

6 x

lo3

Man

sdor

f et

al.

(198

2)

Duc

kett

et a

l. (1

980)

Land

fills

C

abs

of b

ulld

ozer

, lo

rries

, cr

anes

, etc

. Bu

lldoz

er

cabi

n

Dum

ping

si

te

Incin

erat

ion

Proc

ess

area

Shre

dder

A: b

,c

A:C P: b

A:

C A,P:

a,b

A: e

9x10

’-9x1

06

lod-

104

lod-

104

lad-

10’

lod-

3 x

lo3

lod-

2 x

lo4

3 x

102-

5 x

104

lod-

103

< 0.

1-5.

4 5

x lo

t-2

x 10

4

4 x

104-

8 x

lo6

lod-

6 x

10’

lod-

4 x

10’

lad-

10’

< 4-

5 x

10s

0.1-

27

O.O

l-0.9

ao

38; q

RD

14; 2

5ao

33; 3

.8au

> 3

x 10

6 8x

10

3Fc

4 x

102F

C

2 x

104r

c 5

x 10

2

2 x

104

104

7 x

104

Met

al

sepa

rato

r D

ensi

fier

Tipp

ing

floor

A:

a,c

> 9

x 10

5 >

10’

2 x

102-

105

7 x

lo’-8

x

10’

Lem

bke

and

Kins

eley

3

x IO

’-4

x 10

’ (1

980;

198

5)

3 x

102-

10

Cro

ok

et a

l. (1

987)

7

x 10

3-7

x lo

4 R

ahko

nen

(199

2)

2 x

103-

7 x

104

lo’-8

x

lo2

103-4

x

106

6 x

lo’--

lo6

8 x

10’

lod-

4 x

lo4

Proc

essin

g ar

ea

Tipp

ing

bays

, sto

rage

bu

nker

s Ti

ppin

g ha

ll

A: b

,c

A: b

,c

Bunk

er

hall

Cab

in

of c

rane

lod-

2 x

lo4

2 x

lo’-

3 x

10s

0.1-

2.6

4 x

103-

9 x

103

0.3-

7.1

2 x

103-

104

0.6

3 x

102-

4 x

102

NJ R

espi

rabl

e du

st;

FC Fe

cal

colif

orm

s;

lod,

lim

it of

det

ectio

n.

aSam

phng

stra

tegy

: A,

are

a sa

mpl

ing;

P,

per

sona

l sa

mpl

ing.

Sa

mpl

ing

met

hod:

a,

liqu

id

impi

nger

; b,

mem

bran

e fil

ter;

c, A

ndcr

sen

six-

stag

e im

pact

or;

e, e

ight

-sta

ge

impa

ctor

.

P

42 O.M. Poulsen et al. / The Science of the Total Environment 168 (1995) 33-56

Table 3 Microorganisms in bulk samples of waste

Type of waste

Source-separated news papers, uncontaminated

Source-separated news papers, contaminated

Bacteria (cfu/g)

Total

102-5 x 103

7 x 103-5 x 105

Gram-negative

< lo’-6 x lo3

4 x 102-5 x 104

Fungi @u/g)

< 102-2 x 103

8 x 102-2 x 105

Endotoxin ( Is/d

Reference

Malmros et al. (1991)

Source-separated cardboard,

uncontaminated

7 x 102-2 x 105 < 102-2 x 103 < lo24 x 104

Source-separated cardboard,

contaminated

1 x 104-2 x 10s 7 x 102-4 x 10’ 2 x 103-6 x 10”

Domestic waste

Glass Paper Unsorted waste

Percolate from biodegradable fraction Compost

108-109 lo*-109

105-106 105 106-10 106 lo’-108 104 FC

108-109 106-109

109-10’0 109-10’0

104 AF

10’ y

107-109

10-300

Gaube et al. (1986)

Mansdorf et al. (1982)

Nielsen et al. (1991; 1994) Weber (1993)

FC Fecal coliforms; AFAspergirrus fumigatus; ‘Yeast.

1986; K&rig et al., 1987; Assmuth and Kalevi, 1993). Odour analysis was also performed to iden- tify the annoying compounds Wan Langenhove et al., 1982). A single report on the analysis of gas from domestic waste landfills which had been in use for various periods of time gives concentra- tions of pollutants and evaluates the odour and environmental impacts (Brookes and Young, 1983; Young and Parker, 1983). The threshold limit values (TLVs) for long term toxicity were ex- ceeded only for benzene, methanethiol, bu- tanethiols and methanol. The main health hazard described was that for fire or explosion due to the high concentrations of hydrogen and methane.

3.2. Sorting plants in general As described in detail in sections 3.3-3.5, pul-

monary problems, ODTS-like symptoms, gastroin- testinal problems and irritation of the eye and mucous membranes of the upper airways have been reported among Danish workers at waste sorting plants (Malmros et al., 1991). In a former

study on 12 employees involved in manual sorting at four waste sorting plants three complained of work-related pulmonary problems (asthma and chronic bronchitis) with cough and sneezing (Petersen, 1988).

Ettala et al. (1989) used a grading score of l-5 to describe the risk of developing different mus- culoskeletal problems. Back injuries due to sort- ing of waste had a score of 5 indicating that this type of work frequently results in back injuries in Finland. In accordance, Petersen (1988) found a high prevalence of ergonomic problems among workers engaged in the manual sorting of waste. The results should be considered only qualita- tively, since it is hardly possible from interviews of a number of workers to make quantitative estimations of exposure levels.

3.3. Plants sorting unseparated domestic waste General description of technology. In Denmark, a

plant has been designed to receive unseparated domestic waste which is delivered to a pit in the

O.M. Poulsen et al. /The Science of the Total Environment I68 0995) 33-56 43

tipping hall (Petersen, 1988; Malmros et al., 1992). Conveyors from the pit feed the waste to shred- ders and then to mechanical separators to obtain four fractions: the magnetic metal fraction; the biodegradable fraction which is further processed to compost; the fraction for incineration (paper, cardboard and plastics) which is compressed into pellet form for shipment to power plants; and the remaining fraction (inorganic materials such as sand, glass fragments, etc.) which is transported to landfills. Plants with a similar technology exist in, for example, the US (Apotheker, 1991), Ger- many and the UK.

Health problems. None of the 20 workers at an experimental plant sorting unseparated domestic waste showed any signs of respiratory diseases, neither did they show a positive skin prick test against a series of mould antigens present in the work environment, but 10 of the 20 workers had precipitating antibodies against one or several of the mould antigens used (Constable and Ray,

1979). In contrast, nine out of 15 workers man- ually sorting unseparated domestic waste at a Danish plant developed severe lung problems af- ter a mean employment period of 6 months (Malmros et al., 1992). The diagnosis was asthma in eight cases and chronic bronchitis in one case. Two years after having left their jobs, six out of the eight cases with asthma were still complaining of exercise-induced asthma, whereas two had no symptoms.

Exposure. Constable and Ray (1979) measured bioaerosol exposure at the experimental plant mentioned above. At all sites studied Penicillium spp. were found to be predominant ranging in concentration from 5.8 X lo4 to 5.0 X lo6 spores/m3. Cladosporium spp., Aspergillus fumiga- tus and Aspergillus nidulans were also frequently isolated.

To prevent further incidents at the Danish plant which had several cases of severe lung problems, the plant was rebuilt in late 1987 (Table 4)

Table 4 Concentrations of bioaerosols in air samples from a plant sorting unseparated household garbage

Workplace Sampling techniquea

Dust Bacteria (cfu/m3> (mg/m3) Total

Fungi (cfu/m3) Endotoxin Reference

Gram-negative hg/m3)

Tipping hall A: c,d (S 87Jb >5x103-~2x10~ >6x103 > 103-l x 104 480 Malmros et al. A: c,d (M 88) 4 x 103-8 x lo3 lod-4 x lo3 2 x lo3-1 x lo4 < lod (1991;1992) A,P: a,b (J 89) 0.32-4.85 2 X 104-3 X lo5 1 x 103-9 x lo3 6 x 103-1 x lo5 0.2-3

Front end A: c,d (S 87) loader in P: c,d (M 88) 2 x 103-4 x 102 1 x 103 lod-3 x lo3 < lod

tipping A: a,b (J 89) 0.29-0.31 2 X 103-4 X lo3 < 5 x 102 2 x 103-l x 104 0.2 hall

Magnet A: c,d (S 87) >5x103->104 8 x lo3 > 103-> 104 5.50 A: c,d (M 88) 8 x 103-8 x 104 2 x 103-2 x lo4 2 x 103-2 x lo4 < lod A: a,b (J 89) 0.16-0.18 2 X 103-2 X lo4 6 x 102-4 X lo3 7 X lo’-1 X lo3 0.2

Manual A: c,d (S 87) >5x103-~2x10~ >6x103 > 103-104 480 sorting A: c,d (M 88) 1 x 103-5 x 104 1 x 103-2 x 103 1 x 103-2 x 104 110

A: a,b (J 89) 1.02 2 x 105 < 5 x 102 1 x 105 2 Pellet A: c,d (S 87) 990 compactor A: c,d (M 88) 5 x 103-l x 104 8 x lo*-2 x lo3 2 x 103-8 x lo3 < lod

A: a,b (J 89) 0.08-0.5 (2)3 X 103-9 x lo3 1 x 103-2 x 10s 9 x 102-7 x 10s 0.2

lod, limit of detection. “Sampling strategy: A, area sampling; P, personal sampling. Sampling method: a, liquid impinger; b, membrane filter; c, Andersen six-stage impactor; d, RCS (Reuter centrifugal sampler).

b(S 87), September 1987, before rebuilding the plant; (M 88), March 1988, after rebuilding the plant; (J 89), June 1989, 1 year later.

44 0.44. Poulsen et al. /The Science of the Total Environment 168 (1995) 33-56

(Malmros et al., 1990; 1991; 1992). Before re- building large quantities of airborne microorgan- isms and endotoxin were measured at several work processes and the concentrations of endo- toxin ranged from 480 to 990 ng/m3, which is considered to be sufficiently high to cause acute pulmonary effects (Rylander, 1987). These endo- toxin exposure levels have been associated with impaired lung function among workers at cotton mills, pigs and poultry farms and animal feed mills (Table 1). Rebuilding of the plant at first resulted in a substantial reduction in the airborne concentration of microorganisms and endotoxin (March 1988). However, in June 1989 the mea- sured concentrations of airborne fungi at the manual sorting process were surprisingly high considering that the activity at the plant was low during this period (Malmros et al., 1991). It may be concluded that if a plant is not designed to prevent bioaerosol exposure, manual sorting of unseparated domestic waste may pose a high health risk to the workers.

3.4. Paper and cardboard sorting plants General description of technology. Some plants

are designed exclusively to handle source-sorted, clean and dry paper from private households and paper and cardboard collected from offices (Petersen, 1988; Malmros et al., 1991). At such plants the material is received in a tipping hall and a front end loader is used to move the material onto a conveyor belt leading to the pro- cessing area. Manual sorting at the conveyer belt may either be negative, i.e. unwanted materials such as plastic bags can be removed from the main stream, or positive, i.e. the recyclable paper and cardboard materials can be diverted to give different quality fractions. The sorted fractions are transported to balers and the bales are shipped off to paper mills.

Health problems. The Danish cross-sectional study in 1989 included 33 workers employed at two paper sorting plants (Malmros et al., 1991). The workers did not show a higher prevalence of lung problems, gastrointestinal symptoms (nausea, diarrhoea, vomiting) or irritation of the eyes and skin compared with workers at water supply plants. However, serum IgE concentrations were

significantly lower among the paper sorting work- ers, indicating that a healthy worker selection may have occurred.

Exposure. In the Danish study (Malmros et al., 1990, airborne dust was generally below the cur- rent Danish OEL for organic dust, total microor- ganisms only exceeded lo4 cfu/m3 in the tipping hall and Gram-negative bacteria only exceeded lo3 cfu/m3 in the tipping hall and in manual sorting of paper and cardboard (Table 5). Total airborne fungal spores and endotoxin were low at all work processes studied. Further, it was demon- strated that the emission potential of microorgan- isms from clean paper and cardboard waste was low, but contamination of separated paper and cardboard with wet domestic waste may increase the bioaerosol emission potential of the waste by several orders of magnitude (Table 3) (Malmros et al., 1991). Considering these relatively low ex- posure levels, a high prevalence of health prob- lems should not be anticipated among workers sorting clean, dry paper and cardboard, but a risk may exist when the paper and cardboard is con- taminated with wet domestic waste.

3.5. Plants sorting source-separated domestic waste General description of technology. Some plants

are designed to receive source-separated fractions which may contain paper, cardboard, plastics, glass and metals (Petersen, 1988; Malmros et al., 1991). In such plants mechanical separation using mag- netic separators and air classifiers are used to divide the waste into material streams, e.g. glass, metals and paper/plastics. The latter is divided into final fractions of paper, cardboard and reusable plastic materials by positive manual sort- ing at the conveyer belt.

Health problems. The Danish cross-sectional study in 1989 included 23 workers employed at plants sorting source-separated domestic waste (Malmros et al., 1991). The workers at these plants had a significant OR for gastrointestinal symptoms (nausea, diarrhoea or vomiting) (OR = 7.3; C.I.,,.INF% = 2.5; 21.3) compared with workers at water supply plants (n = 119). The OR for itching of the eyes and skin was 3.8 (C.I.,,, = 1.6; 9.4) and 14.7 (C.I.,,, = 1.5; 132.21, respectively. The number of atopic per-

Table

5

Con

cent

ratio

ns

of b

ioae

roso

ls in

air

sam

ples

fro

m p

lant

s so

rting

pa

per

and

sour

ce-s

epar

ated

ga

rbag

e

Type

of

plan

t W

orkp

lace

Sa

mpl

ing

Dus

t Ba

cter

ia

(cfu

/m3)

Fu

ngi

(cfu

/m3)

En

doto

xin

Ref

eren

ce

tech

niqu

ea

(mg/

m3)

To

tal

Gra

m-n

egat

ive

(ng/

m3)

Pape

r Fr

ont

end

load

er

in t

ippi

ng

A: a

,b

1.17

-1.4

4 2

x 10

3-8

x lo

4 3

x 10

3-2

x IO

4 5

x 10

3-9

x 10

” 0.

1-l

Mal

mro

s et

al.

sorti

ng

hall

(199

1)

Man

ual

sorti

ng

A: a

,b

0.38

-1.5

9 2

x 10

3-5

x 10

3 9

x 10

2-5

x lo

3 4

x lo

’-2

x lo

4 0.

1-6

Pape

r or

car

dboa

rd

Mac

ulat

ion

A: a

,b

0.6-

1.23

0.

6 x

lo’-3

x

lo3

lod-

2 x

lo3

lod-

3 x

lo3

0.6-

l Ba

lers

A:

a,b

0.

5-2.

0 3

x 10

3-l

x 10

” lo

d-5

x lo

3 1

x 10

3-l

x lo

4 0.

1-3

Sour

ce

Tipp

ing

hall

A,P:

a,b

0.

23-2

.73

6 x

lo*-4

x

lo4

lod-

8 X

lo3

8 x

lo’-3

x

lo4

0.2-

8 M

alm

ros

et a

l. se

para

ted

(199

1)

dry

hous

e-

Fron

t en

d lo

ader

in

tip

ping

A:

a,b

0.

2-0.

77

8 x

lo*-5

x

lo4

lod-

1 x

lo3

lod-

1 x

lo4

0.1-

5 ho

ld g

arba

ge

hall

(mixe

d M

anua

l so

rting

A,

P: a

,b

< 0.

01-1

.03

lad-

6 x

lo4

lod-

6 x

IO4

lad-

2 x

lo4

< 0.

2-11

pa

per,

card

Ba

lers

A:

a,b

0.

6-1.

13

7 x

103-

6 x

lo4

1 x

103-

4 x

lo4

1 x

103-

2 x

104

0.3-

15

boar

d,

plas

tics,

etc

)

lad,

lim

it of

det

ectio

n.

“Sam

plin

g st

rate

gy:

A, a

rea

sam

plin

g;

P, p

erso

nal

sam

plin

g.

Sam

plin

g m

etho

d:

a, li

quid

im

ping

er;

b, m

embr

ane

filte

r; c,

And

erse

n si

x-st

age

impa

ctor

; d,

RC

S (R

eute

r ce

ntrif

ugal

sa

mpl

er).

46 O.M. Poulsen et al. / The Science of the Total Environment 168 (1995) 33-56

sons among the 23 workers was significantly lower than in the control group, indicating that a healthy worker selection may have occurred.

Exposure. Table 5 summarizes the results of measurements of bacteria, fungi, endotoxin and dust at four Danish plants sorting dry source-sep- arated domestic waste (mixed paper, cardboard, plastics, glass, etc.) (Malmros et al., 1991). In general airborne dust was below the Danish OEL for total organic dust, and total airborne fungal spore was low at all the work processes studied. Total microorganisms occasionally exceeded 4 X

lo3 cfu/m’ at all work processes examined, and sometimes Gram-negative bacteria exceeded lo4 &t/m” and endotoxin exceeded 10 “g/m3 near the manual sorting and near the balers. It may be anticipated that manual sorting and baling of source-separated domestic waste may pose a health risk for workers.

3.6. Other sorting and recycling plants (glass, plastics, metals, etc. 1

Plants for recycling of source-sorted glass have existed for years in many countries, e.g. the Netherlands, France and Denmark, but to our knowledge no studies have yet been published on occupational health problems and exposures in relation to the recycling of glass. If manual sort- ing is performed musculoskeletal problems (shoulder and neck pain, etc.) may occur and, depending on the design of the plant, exposure to noise may be a problem.

In several countries, e.g. the Netherlands and Germany, aluminium tins are widely used for beer and soft drinks. Also in this case no studies have, to our knowledge, been published on occu- pational health problems and exposures related to the recycling of metal tins.

3.7. Compost and biogas producing plants General description of technology. Several dif-

ferent systems for low and high technology com- posting exist (Malmros et al., 1991; Schutte et al., 1991). The biodegradable materials are in general shredded before composting, and when the com- post process is finished, the compost is sieved to remove large items including materials which are not biodegradable.

In the simple low technology composting plants, the piles are established outdoors with no equip- ment for aeration. After a period of several months to years during which the piles are agi- tated mechanically, the compost is sieved and subjected to final cornposting. Due to the low content of structural materials in the biodegrad- able fraction of domestic waste, it is difficult to maintain an efficient composting process in this fraction. Therefore, the biodegradable fraction of domestic waste is often mixed with garden waste or with other biodegradable fractions such as sewage sludge and slurry from livestock buildings.

The principal steps in biogas production are shredding of the biodegradable waste and mixing with water. The mixture is fed to the reactor for anaerobic digestion at reactor residence times of w lo-20 days. The digester effluent is dewatered. The liquid is re-used for the process and the sludge is shipped either to disposal, e.g. as ‘earth’ cover materials at landfills, or used as material for compost production.

Health problems.To our knowledge no studies have been reported on occupational health prob- lems and exposures related to the production of biogas from biodegradable domestic waste.

As emphasized by Boutin and Moline (19861, data on occupational health problems and expo- sures related to composting of domestic waste are much rarer than data on sewage sludge compost- ing. However, Clark et al. (1983) suggested, that occupational health problems may be due to the nature of the process itself and therefore may not be related to the use of wastewater sludge in the composting process.

A series of detailed studies on occupational health problems and bioaerosol exposures in rela- tion to composting of sewage sludge have been performed in Sweden and in the USA. In 1983 the two research groups synthesized their obser- vations by identifying a major group of clinical symptoms for compost workers: more or less fre- quent fever, influenza-like symptoms, upper air- way irritation, eye inflammation and asthenia (Ry- lander et al., 1983).

Lundholm and Rylander (1980) reported that four out of 13 workers at a plant composting mixed sewage sludge and biodegradable domestic

O.M. Poulsen et al. / The Science of the Total Environment 168 (1995) 33-56 47

waste had ODTS-like symptoms such as headache, fatigue, nausea and diarrhoea. The ODTS-like symptoms may arise shortly (e.g. a few hours) after the beginning of the work and they have often disappeared the next morning. Similar health problems were later reported in the Dan- ish cross-sectional study, i.e. gastrointestinal symptoms (nausea, diarrhoea or vomiting) were significantly more frequent among workers at gar- den compost plants (OR = 7.5; C.I.,,., = 1.2; 48.1) compared with workers at water supply plants (Malmros et al., 1991). Lundholm and Ry- lander (1983) stated that such symptoms are fre- quently reported among sewage workers, who are also exposed to high numbers of airborne Gram- negative bacteria, reinforcing the hypothesis that these symptoms may be caused by exposures to high quantities of airborne Gram-negative bacte- ria or endotoxin.

Clark et al. (1984) reported that personnel working at sewage sludge compost operations were exposed to a variety of Gram-negative bac- teria and fungi. These persons showed elevated levels of IgG antibodies against compost-derived LPS. In addition, higher white blood cell counts, elevated levels of C-reactive protein, an acute phase protein, and activation of complement fac- tor C3 were also observsed. Vincken and Roels (1984) reported a case of a 20-year old worker, who after 2 months of employment at a compost plant developed allergic alveolitis and invasive aspergillosis against A. fumigutus. The worker had a high serum titre of precipitating antibodies against this fungus. Weber et al. (1993) described a 52-year old male worker who 12 hours after shovelling composted wood chips and leaves de- veloped hypersensitivity pneumonitis and ODTS. Precipitating antibody tests were inconclusive.

The health damaging potential of compost dust was scrutinized by Frazer et al. (1993) who ex- posed guinea pigs to aerosolized leaf/wood com- post dust containing high spore counts (106-lo9 spores/m31 and substantial endotoxin contamina- tion (- 16300 EU endotoxin/m3). Breathing rates were increased (17%) and trapped gasses, reflecting airway obstruction, was noted. Bron- choalveolar lavage showed that granulocyte infil-

tration increased 5.5-fold immediately after expo- sure, increasing to 16-fold 18 h after exposure.

Exposure.Tables 6 summarizes the results of measurements of bacteria, fungi, endotoxin and dust at different compost plants.

Weber et al. (1993) measured high concentra- tions of fungal spores, Gram-negative bacteria and endotoxin both under routine and worst case conditions, indicating that these may be the cause of the reported case of acute pulmonary symp- toms (Table 6). Lacey and Williamson (1993) col- lected personal and area samples to characterize in detail the bioaerosol exposure at different work tasks at a domestic waste composting plant. High concentrations of fungal spores, thermophilic actinomycetes and bacteria in the air were mea- sured (Table 6). For example, the concentration of Aspeq$lusfimigatus, an allergenic and oppor- tunistic pathogenic mould, usually exceeded 10’ cfu/m3 and sometimes lo6 &i/m”. In a similar study at a pilot scale high technology plant for domestic waste composting, Lacey et al. (1990) sampled airborne microorganisms from indoor sites in the processing plant (Table 6). The num- ber of airborne microorganisms were greatest at the post-compost processing as compared with processing of the domestic waste. From personal sampling in domestic waste composting Lacey et al. (1992) found dust concentrations x=- 10 mg/m3 air (Table 6). Also in this study, high quantities of Aspergillus fumigatus were measured (Table 61, and the authors considered this a potential risk factor for the development of asthma, alveolitis and infection. In agreement, Clark (1986) stated that during cornposting Aspergillus jkmigatus and Penicillium species are some of the most abun- dant fungi.

Compared with the high airborne concentra- tions of fungi reported by Weber et al. (1993), Lacey and Williamson (1993) and Lacey et al. (1990: 1992), the concentrations at different work tasks at Danish compost plants were in general low (Malmros et al., 1991) (Table 6), but the concentrations were in agreement with those re- ported by Clark (1986). In general, Malmros et al. (1991) demonstrated low quantities of Gram- negative bacteria and endotoxin. The discrepancy between the studies may be due to differences in

Tabl

e 6

Con

cent

ratio

ns

of b

ioae

roso

ls in

air

sam

ples

fro

m c

ompo

stin

g pl

ants

Type

of

Wor

kpla

ce

Sam

plin

g D

ust

Bact

eria

(c

fu/m

3)

Fung

i (c

fu/m

”) En

doto

xin

Ref

eren

ce

com

post

ing

tech

niqu

e”

mg/

m3

Tota

l G

ram

-neg

ativ

e Th

erm

ophi

lic

actin

omyc

etes

(n

g/m

3)

Out

door

Indo

or

Out

door

Han

d lo

adin

g of

co

mpo

stin

g

Pre-

com

post

ing

- lo

adin

g co

ntai

ners

fro

m c

onve

yor

Post

-com

post

ing

load

ing

cont

aine

rs

from

con

veyo

r

Dig

ging

w

aste

Turn

ing

com

post

Shak

ing

conv

eyor

A: a

,b

P: b

A: c

P:

b

A: c

A: c

A: a

P:

b

A: c

A:

a

P: b

AC

P: b

Dis

man

tling

5 m

upw

ind

A: a

co

mpo

st

pile

10

m d

ownw

ind

A:a

Nex

t to

pile

P:

b

Wor

ker

on p

ile

P: b

W

orke

r sc

reen

ing

P: b

co

mpo

st

Hou

seho

ld

Load

ing

garb

age

A: c

ga

rbag

e m

ixed

M

ill ou

tlet

with

se

wage

C

ontro

l ro

om

sludg

e

0.7-

150

6 x

lo’-8

X

10s

32-4

0 4

x lo

”-2

x lo

6 2

x 10

3-9

x 10

3 2

x lo

5

6 x

104-

2 x

lo5

2 x

103-

8 x

lo3

5 x

104-

6 X

lo4

42-8

1 4

x 10

6-2

x 10

” 3

x 10

2-9

x 10

s 10

7-2

x 10

8

3 x

105-

5 x

10’

2 x

104-

6 x

lo4

2 x

lo’-2

x

lo6

2 x

106

8x

lo3

2x

106

5 x

10s

192

2 x

106

2 x

106

2 x

10s

165

6 x

lo6

3 x

104

270

9 x

106

3 x

105

1 x

10s

3 x

109

7 x

103

1 x

10s

4 x

103

5 x

103

2 x

10s

3 x

103

6 x

lo5

7 x

106

8 x

10’

4 x

105

3 x

106

6 x

lo4

3 x

106

1 x

106

1 x

lo6

8 x

lo3

4 x

106

8 x

lo6

7 x

104

5 x

106

1 x

10’

2 x

10s

8x

O6

4 x

106

7 x

104

6 x

lo6

> 3

x 10

4

3 x

104-

5 x

10s

7 x

102

7 x

102

1 x

106-

5 x

10s

50-1

200

Web

er e

t al.

(199

3)

4 x

104-

2 X

lo5

Lace

y et

al

(199

0)

3 x

104-

9 x

104

2 x

106-

10’

3 x

105-

106

3 x

105

Lace

y an

d W

illiam

son

2 x

104

(199

3)

6 x

lo4

5 x

105

10s

4 x

106

5 x

104

6 x

10’

4 x

104

Lace

y et

al.

(199

2)

4 x

10s

7 x

106

8 x

lo6

1 x

106

Lund

holm

an

d R

ylan

der

(198

0)

Table

6

(Con

tinue

d)

Type

of

com

post

ing

Wor

kpla

ce

Sam

plin

g D

ust

tech

niqu

e”

mg/

m3

__--

Bact

eria

(c

fu/m

3)

Fung

i (c

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50 O.M. Poulsen et al. / The Science of the Total Enuironment I68 (1995) 33-56

the type of composting plant and, perhaps more important, due to differences in sampling strategy and analytical methods. In the Danish study only a few measurements were carried out at digging, turning or disabling the compost piles, but these few measurements revealed concentrations of air- borne microorganisms similar to those reported by the other groups of researchers (Table 6). Biodegradable domestic waste may have a high emission potential of Gram-negative bacteria and endotoxin (Table 2) (Nielsen et al., 1991: 19941, and at one plant composting biodegradable do- mestic waste, a series of measurements in the control room next to the tipping hall and reactor revealed high airborne concentrations of Gram- negative bacteria ( N lo5 cfu/m3) and endotoxin (N 30 ng/m3) (Malmros et al., 1991).

It may be concluded from the currently avail- able data, that exposure to fungi at several of the processes may range between 105-10’ cfu/m”. Exposure to such levels of airborne fungal spores resulted in pulmonary problems and ODTS-like symptoms in a study on saw mill workers (Eduard et al., 1993). Data on the concentration of air- borne viable Gram-negative bacteria and ther- mophilic actinomycetes varied between the dif- ferent studies, but exposures to Gram-negative bacteria > lo4 cfu/m” were frequently reported. According to Rylander et al. (1983) such high exposures to Gram-negative bacteria can be con- sidered potentially harmful. In several studies ex- posure to thermophilic actinomycetes was within the range lo’-10’ cfu/m”, and Lacey et al. (1990) suggested that exposure levels > lo6 cfu/m3 may pose a risk of extrinsic allergic alveolitis in sensi- tized individuals, and perhaps a risk of ODTS.

A few papers report analysis of VOCs from compost. Up to 5.0 mg/m3 methanethol, 4.2 mg/m3 ammonia and 2.8 mg/m3 hydrogen sul- phide was measured during the first 2 weeks of storage of biodegradable domestic waste, and hy- drocarbons, acetic acid, dimethyl sulphide, li- monene and siloxanes were all present (Nielsen et al., 1991). In a study on the environmental impact of cornposting, Schildknecht and Jager (1978) identified 93 VOCs in compost from household waste. The most prominent VOCs were diacetyl, tetrachloroethylene, dimethyl disulfide,

limonene and benzaldehyde. In another study 21 VOCs were identified but they were only con- sidered part of an odour nuisance (Krauss et al., 1992). Four sulphur compounds have been fre- quently found in air near dumps, sewers and compost installations; hydrogen sulphide, methanethiol, dimethyl sulfide and dimethyl disulfide. OELs for these compounds are N 10 mg/m3. At concentrations > 10 ppm eye irrita- tion and respiratory effects are observed (Glass, 1990). The World Health Organization lists 7 pg/m3 average for 30 min as a guideline for annoyance reactions for hydrogen sulphide (WHO, 1989). The odour detection threshold value is lo-20 pg/m3, making such studies dif- ficult due to the psychological effects. From the food spoilage aspect, only one investigation re- ports VOC concentrations in anaerobic spoilage (Kamiya and Ose, 1984). Here, up to 3900 mg/m3 dimethyl disulphide and 2000 mg/m3 methanethiol, 1400 mg/m3 hydrogen sulphide and up to 4000 mg/m3 of various volatile fatty acids (acetic-hexanoic) were found during the first 2 weeks of spoilage in different foods. It should not a priori be ruled out that accidental anaerobic composting of biodegradable domestic waste, which may occur if the content of structure mate- rials in the compost is low, may lead to the emission of organic sulphur in quantities suffi- ciently high to cause, e.g. irritation of the eye.

4. Future research activities

4.1. Dose-response relationships between exposures and adverse health effects

Based on the current knowledge, the major occupational health problems among workers at waste recycling plants are pulmonary disorders, ODTS-like symptoms, gastrointestinal problems, eye inflammation, irritation of the skin and upper airways and musculoskeletal problems. However, limited information exists on the magnitude of the risks and the causal factors of these occupa- tional health problems, particularly in relation to different types of waste recycling plants and the different work tasks within.

Musculoskeletal problems. The current limited knowledge on musculoskeletal problems among

O.M. Poulsen et al. / The Science of the Total Environment 168 (1995) 33-56 51

workers at waste recycling plants indicates a high incidence of lower back injuries due to heavy lifts during work at landfills and incineration plants, as well as various musculoskeletal problems due to multiple repetitions of movements in stooped postures with torsion of the body during manual sorting of waste. However, no field studies have yet elucidated how often musculoskeletal prob- lems occur in relation to different factors which may govern the work conditions of workers at waste recycling plants, e.g. types of work organisa- tion, equipment, host factors, etc. In this context several methodological problems exist, and simple standardized observation and measurement meth- ods are needed to evaluate the mechanical and energetic load at different work conditions.

Pulmona y, gastrointestinal, mucous membrane and skin problems. When considering the available information, it becomes apparent that a good deal of knowledge exists on potentially dangerous exposures in the work environments currently re- ceiving most of the domestic waste, i.e. transfer stations, landfills and incineration plants. Infor- mation also exists on exposures at plants sorting paper/cardboard and mixed domestic waste, but to our knowledge no information is available on exposures in the sorting and recycling of glass, metal tins and plastic materials. Regarding the recycling of the biodegradable fraction of domes- tic waste, information is available on exposures at composting plants, whereas no information exists on plants producing biogas from biodegradable domestic waste.

Several studies support the hypothesis that ex- posure to microorganisms and the toxic products thereof are important factors causing a multitude of different symptoms among workers at waste sorting and recycling plants, i.e. pulmonary dis- orders, ODTS-like symptoms, gastrointestinal symptoms, eye inflammation and irritation of the skin and mucus membranes of the upper respira- tory airways. The available data on aerosol expo- sures and health problems in the waste sorting recycling industry indicate important differences depending on the type of plant:

1. Workers at transfer stations, landfills and in- cineration plants may have a high prevalence

of pulmonary disorders and gastrointestinal problems (Table 2). Exposure to dust exceed- ing existing OELs was observed at refuse transfer stations and at incineration plants when emptying cinders or working with shredders. At transfer stations, landfills and incineration plants high concentrations of to- tal airborne bacteria, coliform bacteria, fecal coliform bacteria and fungal spores have been reported.

2. Workers involved in the manual sorting of unseparated domestic waste may have a high risk of pulmonary diseases (asthma, bronchi- tis, allergic alveolitis), ODTS-like symptoms, gastrointestinal problems and irritation of the eye and mucous membranes of the upper airways. This type of work may be associated with exposures to large quantities of airborne microorganisms and endotoxin (Table 4).

3. At plants sorting and recycling source-sep- arated domestic waste the workers may have a high risk of gastrointestinal symptoms and irritation of the eyes and skin. At such plants the bioaerosol exposure levels are in general low, but at some work tasks, e.g. manual sorting and work near the balers, high expo- sure levels may occur (Table 5).

4. The few existing reports on workers at paper sorting plants indicate that handling source- sorted paper and cardboard, e.g. from offices, does not involve an elevated risk of occupa- tional pulmonary problems, gastrointestinal symptoms or irritation of the eye or skin as compared with workers in general, and levels of bioaerosol exposures at such plants are in general low (Table 5).

5. Workers at compost plants experience more or less frequent fever, influenza-like symp- toms, upper respiratory tract irritation, eye inflammation, asthenia and gastrointestinal symptoms such as nausea and diarrhoea. In addition, cases of severe occupational pulmo- nary diseases, i.e. asthma and aspergillosis, have been reported among compost workers. Several of the work processes at compost plants develop high concentrations of air- borne fungal spores and thermophilic acti- nomycetes (Table 7).

52 O.M. Poulsen et al. / The Science of the Total Environment 168 (1995) 33-56

4.2. Interaction between airborne exposures Workers at waste sorting and recycling plants

may be exposed to a complex mixture of bioaero- sols and airborne volatile compounds, and syner- gistic interactions between the agents may be of importance. Exposure to endotoxins may through their adjuvant effects make allergens more potent with respect to sensitization and triggering of allergic reactions (Nom et al., 1986; 1990). Fi- nally, it is believed that exposure to irritants may increase the sensitivity to other airborne pollu- tants, e.g. allergens and microbial endotoxins.

Since bioaerosols in the work environment of workers at waste sorting and recycling plants con- tain many potentially dangerous agents, it may be useful to measure the overall biological activity of such mixtures in addition to the traditional mea- surements of the single agents. Many of the ad- verse health effects seem to be connected with an inflammatory response in the host. An assay mea- suring the overall inflammatory potential of an aerosol sample would be valuable in the risk evaluation of exposure to complex bioaerosols. The basic methodology may already exist since several assays based on in vitro stimulation of cells have been described, using murine macrophages (Hindahl et al., 1990; Kelly et al., 1990, human epithelial cells (Hedges et al., 1992), human blood mononuclear cells (Hindahl et al., 1990) and human blood basophilic granulocytes (Nom et al., 1986; 1990).

4.3. Occupational exposure limits for bioaerosol exposure

Currently, specific agents causing health prob- lems among workers in the waste sorting and recyling industry have not yet been identified.

Boutin and Mouline (1986) stated that airborne microbial exposures to workers at landfills, incin- eration plants, waste sorting plants and compost- ing plants differ only by degree and not by nature, and the authors suggested that the ‘compost worker syndrome’ (frequent fever, influenza-like symptoms, upper airway irritation, eye inflamma- tion. asthenia) may occur among workers at these plants. In accordance with this, Clark et al. (1983) suggested, that occupational health problems among workers at compost plants are due to the

nature of the process itself and therefore may not be related to composting of different materials such as garden waste, sewage sludge, etc. It may thus be suggested, that the etiology of the differ- ent symptoms is essentially the same, and that the different symptoms emerge when susceptible indi- viduals respond to different exposure levels. To include all types of plants the authors of the current review consider the term ‘waste recycling worker syndrome’ to be more appropriate. If the hypothesis of a waste recycling worker syndrome is supported by future investigations, it may be possible to identify a few markers of bioaerosol exposure which can be easily measured and used in the establishment of OELs for the waste sort- ing and recycling industry.

As outlined in Table 1, data supporting the exposure-effect relationship has accumulated for exposure to endotoxin and various microorgan- isms in other industries. Tentative OELs (section 3) have been suggested for endotoxin in cotton mills (Rylander, 1987; Castellan et al., 1987) and some studies have indicated exposure levels of, e.g. mould spores, which may give rise to pulmo- nary symptoms, mucous membrane irritation and ODTS-like symptoms (Eduard et al., 1993; Malm- berg et al., 1988). Since the development of occu- pational allergic asthma is highly dependent on the individual susceptibility, it may not be possi- ble to suggest tentative OELs for fungal spores in relation to this disease. It is tempting to suggest that the OELs for workers at waste sorting and recycling plants should be lower than those for cotton mill workers. Compared with cotton mill workers the aerosol exposure of workers at plants recycling the biodegradable waste fraction is more complex with simultaneous exposure to a variety of microbial agents which may act in concert, i.e. Gram-negative bacteria and endotoxin, ther- mophilic actinomycetes, moulds and p-1-3- glucans, allergens, volatile organic compounds, etc. (section 4.2.). Further, it should be empha- sized that the proposed tentative OEL values do not take into account the following problems:

Total versus inhalable airborne exposure. When the hazard of breathing an atmosphere contain- ing bioaerosols is evaluated, sampling of the

O.M. Poulsen et al. /The Science of the Total Environment 168 (1995) 33-56 53

inhalable fraction rather than the ‘total’ bioaerosol fraction should be preferred. How- ever, several of the reviewed publications re- port ‘total’ bioaerosol concentrations, and only a few reports give information in terms of the concentration of inhalable aerosols. Viable versus total microorganisms. Many prob- lems exist with the presently available bioaero- sol samplers, most notably with the way they physically collect aerosols and with their biolog- ical viability effects on the sampled aerosol (Smid et al., 1989; Nevalainen et al., 1992). Since the health problems may be associated with both viable and non-viable microorgan- isms, measurement of total microorganisms should be preferred. However, the majority of the reviewed publications only report cultur- able microorganisms and data on exposure to non-culturable microorganisms is very sparce. The viability of different microorganisms dur- ing sampling is dependent on the employed sampling equipment (impactors, implinger, fil- ters, etc.) @mid et al., 1989; Navalainen et al., 1992). Boutin and Mouline (1986) and Malm- berg (1991) emphasized the lack of standard- ized procedures both for the sampling of bioaerosols and for the establishment of viable or total counts of microorganisms. Static area air sampling versus personal air sam- pling. Much of the data reported in the re- viewed publications were obtained by static area sampling. Cohen et al. (1984) compared results obtained with personal air samplers and static area samplers placed in the vicinity of the workers. Generally, the exposure levels ob- tained by personal air samplers were substan- tially higher than the levels obtained with area samplers. Thus, the available exposure data for waste sorting and recycling workers may be too low. Sampling strategy. Particular attention should be paid to the selection of the sampling strategy to prevent misclassification of exposure, i.e. multi- ple measurements of exposures are needed to characterize the exposure profile at each de- fined work task with sufficient accuracy, taking into account the major sources of variation. Heederik (1990) emphasized that the measure-

ment of average airborne exposures should be used in analytical epidemiological studies of bronchitis, whereas peak exposure levels are of greater importance in studies on allergic alve- olitis and asthma. None of the studies on bioaerosol exposures of workers at waste recy- cling plants have attempted to solve the prob- lems related to the selection of sampling strat- egy and exposure classification.

The major research challenge is to describe the causal relationship between a matrix of occupa- tional, potentially dangerous exposures occurring simultaneously and a multitude of adverse health outcomes. To obtain data which can be used for the establishment of OELs for bioaerosol expo- sures in the work environment of waste sorting and recycling plants, detailed analytical epidemio- logical studies and monitoring programmes taking the above mentioned problems into account are needed to elucidate causal links between various bioaerosol exposures and the major health prob- lems.

Acknowledgements

This review is the result of the first phase of a 5-year multidisciplinary research programme sup- ported jointly by the Danish Ministry of the Envi- ronment and the Ministry of Labour. Dr. Jacek Dutkiewicz, Institute of Agricultural Medicine, Lublin, Poland, Dr. Dick Heederick, Department of Epidemiology and Public Health, Agricultural University Wageningen, The Netherlands, Dr. Per Maimberg, Institute of Occupational Health, Solna, Sweden, Dr. Wilhelm Frederiksen, Depart- ment of Clinical Microbiology, Statens Serumin- stitut, Copenhagen, Denmark, Professor Soren Molin, Laboratory for Microbiology, The Techni- cal University of Denmark, Lyngby, Denmark, Associate Professor, PhD Torben Sigsgaard, Insti- tute for Environmental and Occupational Medicine, University of Asrhus, Denmark are greatly acknowledged for their valuable com- ments and suggestions. Furthermore, the research group wishes to express its gratitude to Drs. Ib Andersen, Elsa Bach, Finn Gyntelberg, Gisela Sjogaard, Karsten Wassermann and all others who

54 O.M. Poulsen et al. /The Science of the Total Environment 168 (1995) 33-56

have contributed to this report with information as well as fruitful discussions and suggestions.

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