A P E S C H A P T E R 1 7

TOXICOLOGY

“All substances are poisons: there is none which is not a poison.  The right dose differentiates a poison and a remedy." Paracelsus (1493-1541)

• Risk: probability of suffering harm from a hazard that can cause injury, disease, death or economic loss or damage• Risk assessment: evaluate risk associated with a hazard• Risk management: implement plan of action• Cost-benefit analysis• Risk-benefit analysis

• Biological, chemical, natural, cultural and lifestyle hazards• Hazard: anything that can cause injury, disease, or death to

humans; damage to personal or public property; deterioration or destruction of environmental components

BIOLOGICAL HAZARDS

• Infectious disease (flu, malaria, TB)• Caused by a pathogen (virus, bacteria, protists, fungi, helminths--

worms)

• Transmissible disease (measles, HIV)

• Non-transmissible disease (cancer, asthma, diabetes, malnutrition)• Not caused by pathogen

• Major concerns include flu, AIDS (HIV), Hepatitis B, malaria and emergent diseases (West Nile, Ebola)• 94% of all deaths attributed to infectious disease are from AIDS,

respiratory viruses, and diarrheal disease

BIOLOGICAL HAZARDS

• Factors that contribute to chronic diseases (heart disease, diabetes, emphysema…) more prevalent in developed nations• High blood pressure, tobacco use, high blood glucose, obesity

• In developing countries chronic disease (respiratory and diarrheal infections) risk factors include• Unsafe sex, alcohol use, indoor smoke (cooking fires), unsafe

water, malnutrition

• Eliminate through infectious disease prevention, education, vaccines, improving quality of life and decreasing malnutrition

CHEMICAL HAZARDS

• Toxic chemical: can cause temporary or permanent harm or death to humans or animals• Top 5 include: arsenic, lead, mercury, vinyl chloride (plastics) and PCBs

• Neurotoxin: chemicals that disrupt the nervous system of animals• Insecticide, lead, mercury

• Endocrine disruptor: interfere with normal hormone functioning• Medications, atrazine, pesticides

• Carcinogen: promotes cancer• Arsenic, benzene, formaldehyde, gamma and UV radiation, PCBs, radon, tobacco

smoke, vinyl chloride, asbestos

• Mutagen: increases frequency of mutations

• Teratogen: cause harm or birth defects to fetus/embryo• Alcohol, benzene, formaldehyde, lead, mercury, PCBs, phalates, thalidomide, vinyl

chloride

EVALUATING CHEMICAL HAZARDS

• Toxicity: measure of the harmfulness of the product• Dose: amount ingested, inhaled, or absorbed• Response: damage to health, may be acute or chronic• Depends on age, genetic makeup, solubility of compound

(water vs. oil) and persistence

• Dose-response Studies• Tests on animals with measure doses of chemical• Plot results of chemical tests to determine curve and

lethal doses

LD50

• Lethal dose 50: Amount of chemical that kills 50% of a test population within 18 days. • Varies depending on substance• Determines if a new substance is more or less lethal than other

chemicals used• Usually tested on rats…then extrapolated to humans• Gives values for acute toxicity

• Lower LD50 = More toxic

ENVIRONMENTAL POLLUTANTS

• Pollution: the presence of a substance in the environment that prevents the functioning of natural processes and produces undesirable environmental or health effects• Increases with growing population and expanding use of

resources • Effects can be aesthetic (not pretty), globalized or local

• Pollutant: any material that causes pollution• Usually by-products of normal/essential activities

TOP ENVIRONMENTAL POLLUTANTS

• Asbestos• Indoor air pollutant• From ceiling tiles and pipe

insulation• Impacts human health (lung

cancer, mesothelioma)

• CFCs• Atmospheric air pollutant• From air conditioners and

refrigerators• Impacts ozone layer (greenhouse

gas)

• Carbon Monoxide (CO)• Air pollutant (indoor/outdoor)• From burning of fossil fuels• Impacts atmosphere (weak

greenhouse gas) and human health

• Carbon Dioxide (CO2)

• Air pollutant (indoor/outdoor)• From respiration, combustion

of organic material• Impacts climate change

(greenhouse gas)

• Dioxins• Soil/water pollutant• From industrial processes (by-

product)• Impacts endocrine/immune

system, toxic to animals, bioaccumulation

• Disease Agents• Water pollutant• From animal/human waste• Impacts…

TOP ENVIRONMENTAL POLLUTANTS

• Formaldehyde• Indoor air pollutant• From building materials,

textiles, furniture• Impacts…

• Lead• Air, soil, water pollutant• From industry, gas, paint• Plant/animal impacts

• Mercury• Air, soil, water pollutant• From combustion of coal,

burning, smelting• Mutagenic impacts,

bioaccumulation

• Nox

• Air, water pollutant• From combustion of fossil fuels• Impacts air quality (smog), acid

rain, increase tropospheric ozone

• Oil• Water/soil pollutant• Natural source, surface runoff,

spills• Impacts water quality, aquatic

organisms (toxic)

• Oxygen Demanding Waste• Water pollutant• From sewage, industry,

agriculture• Impacts dissolve oxygen in water

(anoxic)

TOP ENVIRONMENTAL POLLUTANTS

• Ozone • Air pollutant• From photochemical reaction with

NOx and VOCs

• Impacts plants, respiratory irritant (asthma)

• Particulates• Air pollutant• From soot, dust, soil, smoke,

industry• Impacts photosynthesis, air quality

• Pesticides• Air, Soil, water pollutant• From agriculture, golf courses,

urban runoff• Impacts plant/animals, toxic,

bioaccumulates

• Phosphates• Water pollutant• From fertilizer, sewage• Impacts water quality

(eutrophication)

• Radon• Indoor air pollutant• From radioactive decay of

uranium• Impacts human health (lung

cancer)

• Sulfur Dioxide (SO2)

• Air pollutant• From combustion of coal• Impacts air quality (acid

rain), forms smog

LEGISLATION INVOLVED IN MANAGING TOXINS

• FIFRA (Federal Insecticide, Fungicide, Rodenticide Act)—1910 (1972)• Initially set standards for pesticide quality, with little consideration for environmental impact• 1972 shifted to EPA control, and focused on protecting environment and human health

• Clean Air Act--1970• to establish air quality standards designed to minimize the air pollution found most harmful to human health. • Six pollutants were specifically targeted--particulate matter, sulfur dioxide (SO2), carbon monoxide (CO), ozone

(O3), nitrogen dioxide (NOx), and lead (Pb). 

• Clean Water Act--1970• establishes and maintains goals and standards for U.S. water quality and purity• eliminate the discharge of pollutants into rivers, lakes, streams and other waterways

• Toxic Substances Control Act—1976• Gave the EPA the ability to track the 75,000 industrial chemicals currently produced or imported into the United

States. • EPA repeatedly screens these chemicals and can require reporting or testing of those that may pose and

environmental or human-health hazard.

• Stockholm Convention--2001• Seeks to protect human health from the 12 most toxic chemicals (includes 8 chlorinated hydrocarbon pesticides).

• CERCLA--1980• Also known as the "Superfund" Act. This regulates mineral processing wastes. Hazardous wastes dumped

somewhere can also be cleaned up through government funding

THE DIRTY DOZEN

• Aldrin• Dieldrin• Chlordane• DDT• Endrin• Mirex

• Heptachlor• PCBs• Toxaphene• Dioxins• Furans• Hexacholorobenzene

The following chemicals are classified as persistent organic pollutants (POPs)—they persist in the environment and bioaccumulate.

They were identified under the Stockholm Convention of 2001. The US did not ratify this treaty.

NATURAL HAZARDS

• Hurricanes• Floods• Tornadoes• Volcanic eruptions• Earthquakes • Landslides• Forest fires

• Some effects preventable (warning systems, building techniques) others a consequence of where people choose to live

CULTURAL HAZARDS

• Where live• Criminal activity• Political unrest• Economic development of the country• Risk factors differ substantially between

developed/developing (access to food, water, healthcare)

LIFESTYLE HAZARDS

• Engaging in risky behavior• Smoking, drugs, alcohol• Eating too much• Driving too fast• Occupational hazards• sunbathing