Environmental Science

Environmental Science Unit 4 - Risk, Toxicology, & Human Health (STE 7th ed. Chapter 11)

Where are we going? - Types of hazards - Toxicology • Chemical hazards • Biological hazards - Risk Analysis estimating risk, major risks, issues

Types of Hazards • Risk is a measure of the possibility of experiencing a hazard that can cause harm • expressed as a probability; 1 in 200, 1 in 1000 etc.e.g. risk of death from flying in US 1 in 7,000,000 • risk assessment involves estimation of the probability of harm to human health, society, or the environment that may result from exposure to specific hazards • risk management involves the decision to reduce a risk and the costs associated

Types of Hazards Identify the (i) Risk, (ii) Hazard and (iii) Risk Management

Types of Hazards Risk as a Probability NYT Jan 29th 1995 NYT Jan 29th 1995

NOVAHow Risky is Flying? NOVA: Deadliest Plane Crash

Types of Hazards Major Hazards • cultural hazards • chemical hazards • physical hazardsnoise, fire, tornadoes, hurricanes, earthquakes, volcanic eruptions, floods, & ionizing radiation; • biological hazardspathogens, pollen & other allergens, & animals such as bees & poisonous snakes unsafe working conditions, smoking, poor diet, drugs, drinking, driving, flying, criminal assault, poverty; harmful chemicals in air, water, soil, & food;

Causes of DeathAnnual Deaths 3 x 400 passenger jets crashing every day WHO estimates 80 x 106 deaths 1950-2000 3 x more than all wars of 20th century US deaths in 2003

+ many more

MovieThe Realities of Risk (13 of 29 mins) View the following movie:http://vega.org.uk/video/programme/5(part of the series http://www.open2.net/nextbigthing/ Questions: (i) What is risk bootstrapping? (ii) Why does the scientist think it was ‘daft’ to ban the pesticide ‘alar’?

Case Study: A Black Day in Bhopal, India • The world’s worst industrial accident:1984 pesticide plant, Bhopal India. • An explosion at Union Carbide pesticide plant in an underground storage tank released a large quantity of highly toxic methyl isocyanate (MIC) gas. • 15,000-22,000 people died • Indian officials claim that simple upgrades could have prevented the tragedy.

Toxicology • study of the adverse effects of chemicals on health • toxicity: measure of how harmful a substance is; depends on: • dose: amount of a potentially harmful substance ingested, inhaled, or absorbed through the skin; • response: resulting type & amount of damage to health may be acute or chronic Also: frequency of exposure, age, effectiveness of detox systems, genetics

Toxicology

The dose makes the poisonAny chemical be it natural or synthetic can be harmful

Should we be concerned?…traces of synthetic chemicals in our environment • Lack of data • Effects difficult to determine Poor diet + pollution = brain damage Which is major factor? • Life expectancy has increased • Lower levels and new contaminants are being detected due to new technology

Misconception • Misconception that all natural chemicals are safe and all sythentics are bad e.g. fruit seeds and pips form cyanide in the stomach, green potatoes, naturally occuring pesticides, mould/fungi on food

ToxicologyToxicity of Chemicals • Animal testing, case and epidemiological reports • generally defined by LD50 – amount in a dose that kills 50 % of population in 14 days • poison: legally defined as a chemical that has an LD50 of 50 milligrams or less per kilogram of body weight

Table 17–1

ToxicologyResponses • Acute toxicity: • Sudden and severe exposure • Rapid onset of symptoms • Chronic toxicity: • Continuous, long-term exposure • Relatively low dose • Cancer, birth defects, neurological damage Same chemical may show both effects e.g. skin irritation vs. cancer

ToxicologyDose-Response • Acute toxicity tests • design: • Controls (no dose) & treatments (low to high dose) • test organism(usually rats or mice) • replicates (usually 60–200 animals total) • period (often 14 days) High doses are used to reduce no. subjects and increase speed of test - Extrapolated down to low doses 2-5 years, $200,000-$2 million

Dose–Response Curves Any dosage is harmful (Assumed in most cases) Lower limit to harmful dose

Question If a dose of 0.1 μg is sufficient to kill a mouse, what mass would be fatal to you? What average level of substance would have to be present in drinking water for you to receive a fatal dose in one week? Ratio mass human : mouse = 200 : 1 Mass that would kill you = 200 x 0.1 μg = 20 μg 2 L water d-1 x 7 d w-1 = 14L For fatal dose 20 μg / 14 L = 1 μg L-1 = 1 ppb

Toxicology • Complications • Different physiology • Synergestic effects – difficult and expensive to test for 1, no. tests multiply when consider more than 1 • Because of complexity in determining toxicity allowed exposure levels are set 100-1000 x below harmful levels

Toxicology Estimating human exposure to chemicals and their effects is very difficult because of the many and often poorly understood variables involved.

Toxicology • Children are more susceptible to the effects of toxic substances because: • Children breathe more air, drink more water, and eat more food per unit of body weight than adults. • They are exposed to toxins when they put their fingers or other objects in their mouths. • Children usually have less well-developed immune systems and detoxification processes than adults

Toxicology • The U.S. Environmental Protection Agency proposed that regulators should assume children have 10 times the exposure risk of adults to cancer-causing chemicals • Some health scientists contend that regulators should assume a risk 100 times that of adults

Background • Birth defects due to exposure to synthetic chemicals • Toxicity to mammals and birds • Carcinogenic effects • Xenoestrogenic effects • Gt. Lakes cormorant with crossed bill

ES&T Article

Chemical Hazards Toxic chemicals(kill) Hazardous chemicals(harm)

Chemical HazardsToxic Chemicals Temporary or Permanent harm or death: • mutagens: cause random mutations (changes in the DNA) e.g. nitrous acid, UV, γ, α radiation • teratogens: cause birth defects e.g., alcohol, PCBs, steroid hormones, heavy metals • neurotoxins: damage nervous system e.g., DDT, alcohol, heavy metals • carcinogens: cause cancer • over 100 types e.g. benzene, dioxin, radionuclides, asbestos http://en.wikipedia.org/wiki/International_Agency_for_Research_on_Cancer

Hazardous Chemicals cause harm in various ways • flammable or explosive (e.g., gasoline); • irritating or damaging to skin or lungs (e.g., strong acids or alkalis) • interfering with or preventing oxygen uptake & distribution (e.g., carbon monoxide, CO); • inducing allergic reactions of the immune system (allergens)

Dioxin IncidentsTimes Beach, Missouri NYT 121682

Dioxin IncidentsTimes Beach, Missouri 1972-76dirt roads were sprayed with waste oil containing super concentrated dioxin from Agent Orange manufacture 1992 - Town was demolished 1997 - 265,000 tons of soil was incinerated on site Now Route 66 State Park Shown in History Channel Modern Marvels #20

Effects at Low Doses Long-term exposure to some chemicals at low doses may disrupt the body’s: • Immune system: specialized cells and tissues that protect the body against disease and harmful substances. • Nervous system: brain, spinal cord, and peripheral nerves. • Endocrine system: complex network of glands that release minute amounts of hormones into the bloodstream.

Hormone Disrupters • hormones: molecules that act as messengers to regulate various bodily processes, including reproduction, growth, & development (endocrine system) • hormone disrupters: interfere with hormone function • so far 51 chemicals shown to act as hormone disrupters on wildlife, laboratory animals, & humans • e.g., dioxins, certain PCBs, various chemicals in plastics, some pesticides, lead & mercury • 1997 study shows that sperm count of men in U.S. & Europe has declined 50%

Hormone Disrupters Molecules of certain synthetic chemicals have shapes similar to those of natural hormones and can adversely affect the endocrine system

Biomagnification A chemical whose concentration increases along a food chain is said to be biomagnified • DDT concentration in Lake Ontario Trout Biomagnification results from a sequence of bioaccumulation steps

Biomagnification when a chemical becomes concentrated in specific organs or tissues e.g., DDT, dioxin, PCBs accumulates in fatty tissues Known as persistent organic pollution (POP) contributing factors: • organic chemical (like dissolves like) • high persistence • not easily broken down or excreted

Health EffectsEffects in Utero • Exposure to low levels results in impaired intellectual development NYT, September 12th 1998

Health EffectsDioxins, Furans and PCBs in Food • 95% of human exposure to • dioxins and furans is from • the presence of these • compounds from food • Fresh water fish has the • highest level of PCBs • Schecter et al., 1997 NYT July 2nd 2003

Why do we know so little? • Under existing laws, most chemicals are considered innocent until proven guilty, and estimating their toxicity is difficult, uncertain, and expensive. • Federal and state governments do not regulate about 99.5% of the commercially used chemicals in the U.S. • Only 10% of 80,000 chemicals have been tested for toxicity • Chemicals are considered innnocent until proven guilty

Pollution Prevention“better safe than sorry” • Some scientists and health officials say that preliminary but not conclusive evidence that a chemical causes significant harm should spur preventive action (precautionary principle) • Manufacturers contend that wide-spread application of the precautionary principle would make it too expensive to introduce new chemicals and technologies

Pollution and Cancer • Bruce Ames believes that the focus on man-made chemicals as causes of cancer is a distraction from the real threats of smoking and diet • Media: http://www.bruceames.org/bnamedia.html

Environmental Testing • Experiments with test animals are used to determine how carcinogenic a compound is, take many years • The simple Ames test can be used fairly rapidly to distinguish compounds likely to be human carcinogens

Biological Hazards nontransmissible diseases • cardiovascular disorders, cancers, emphysema, & malnutrition; transmissible (infectious) diseases • caused by bacteria, viruses, protozoa, or parasites • colds, flus, hepatitis, sexually transmitted diseases, malaria • many transmissible diseases spreading over broad geographic areas • Lyme disease (bacteria) • Giardia (protozoa)

Environmental Science