High Levels of Dioxins in River Sediments and Cancer Risk in Nearby Farmers: A
Case Study using a GIS application
PK Verkasalo1, E Kokki1, E Pukkala2,
T Vartiainen1, J Pekkanen1
1National Public Health Institute2Finnish Cancer Registry
Background The River Kymijoki is one of the largest rivers in
southern Finland with close to 190,000 people living within 20 km from its shoreline
The sediment levels of dioxins in the river are between 0.5 and 350 ng g-1 (I-TEQ) and thus among the highest in the world
The dioxins originate from the production of a chlorophenol product where they occurred as an impurity
2-3-7-8-TCDD is classified as a human carcinogen by IARC
Hypothesis
We hypothesize that dioxins are mobilized from the river sediments and accumulate in the nearby residents via the food chain
Therefore the people and especially the farmers living closest to the river are suspected to be at the highest risk
We also explore the cancer patterns in people living near the river and the additional effect of living close to the Baltic Sea
Small area statistics on health (SMASH) -system– whole of Finland divided into squares of 0.5 km * 0.5 km
– for each square data on cancers and population counts by background variables (sex, age and social class)
Study design– exposure was defined as distance of residence to the river shoreline in
1980 (<1 km, 1-4 km, 5-19 km)
– follow-up for cancer from 1981 to 2000
Relative risks– from Poisson models with observed and expected cancers adjusting for
sex, age, calendar period, and distance to sea
Methods
Risk of total cancer in all residents River Kymijoki 1981-2000; N=187,800
1,00 1,07 0,99
0,000,200,400,600,801,001,201,401,601,802,00
5-19 km 1-4 km < 1km
Distance to river
RR
s (
95
% C
Is)
Risk of total cancer in farmers River Kymijoki 1981-2000; N=10,800
1,00 0,971,21
0,000,200,400,600,801,001,201,401,601,802,00
5-19 km 1-4 km < 1km
Distance to river
RR
s (
95
% C
Is)
Risk of total cancer in farmers* <1 km to the River Kymijoki 1981-2000; N=1500
SexMen: 1.17 (0.87-1.56)
Women: 1.27 (0.90-1.79)
Age in 19800-44 years: 1.81
(1.16-2.84)
45-59 years: 1.09 (0.78-1.34)
60 years: 1.04 (0.69-1.57)
Calendar period1981-1990:1.40 (1.00-1.97)
1990-2000: 1.09 (0.81-1.46)
Distance to sea40-59 km: 0.94 (0.46-1.95)
20-39 km: 1.46 (1.03-2.07)
<20 km: 1.14 (0.83-1.57)
*RRs and 95% CIs from Poisson models in comparison to the reference zone and adjusting for all other variables
Cancer pattern in farmers <1 km to the River Kymijoki 1981-97; N=1500
testis 4.0
sarcoma 2.9
brain 2.6
skin, non-melanoma 2.4
Hodgkin's disease 1.8
breast 1.8
pancreas 1.7
bladder 1.6
liver 1.5
ovary 1.5
thyroid 1.4
prostate 1.3
rectum 1.3
leukaemia 1.3
oesophagus 1.2
non-Hodgkin lymphoma 1.1
lung 0.93
corpus uteri 0.83
kidney 0.74
colon 0.70
stomach 0.61
skin, melanoma 0.40
Discussion about the method
Exposure assessment is based on the location of residence at one point in time
Rapid analyses can only provide first approximations of risks
In case of negative results, you need to be cautious not to exclude a real effect
In case of positive results, the method provides only limited evidence on causality
Discussion about the results
The results are compatible with a dioxin effect or an effect in reproductive cancers
Some of the risk increases could be explained by alcohol, chemicals or mutagenic drinking water
The results are unlikely to be explained by smoking, dietary habits or solar exposure
Thank you!
