Chapter 4: Environmental Hazards

Derek Muller & Sean McEvoy

"The association between certain chronic diseases and environmental causes is devastatingly clear, yet knowledge about the scope of environmental health risks and their impact on the public's health is limited.“ US Institute of Medicine (2002)http://www.youtube.com/watch?v=OiiVcm8vjDc

Pesticides and Human Development

Pesticide exposure can cause diseases, such as cancers, as well as mental or physical disabilitiesEven affects simplest mental development

Two groups of preschoolers differing mainly in pesticide exposure were asked to draw a person.

Those who were less exposed drew stick figuresThose who were more exposed drew meaningless circles and lines

Riskthe probability of harm, injury, disease, death, environmental damage occurring under certain circumstances.What are some risks you take every day?

Human Decision Making

Risk ManagementWe can’t always rely on intuition, habit, and experience to make a decision Other factors, including health and environmental factors, play a partRisk management- the process of identifying, assessing, and reducing risks

5 Steps of Risk Assessment

1. Hazard identification

Is exposure to this chemical substance harmful?2. Dose-response assessment

What is the relationship between exposure to the substance and its effects?3. Exposure assessment

How much, how long, and how often are people exposed to this substance? 4. Risk characterization

The conclusions are spelled out.5. Risk Management

ToxicityToxicants- chemicals with adverse effectsAcute toxicity- occur within short period after high-level exposure to toxicantChronic toxicity- occur after a long period of low-level exposure to toxicant

Symptoms tend to mimic other chronic diseases associated with risky lifestyle, poor nutrition, and aging

ToxicologyStudies effects of toxicants on living organismsStudies mechanisms that cause toxicityDevelops ways to prevent or minimize adverse effects

EpidemiologyStudying how toxicants, disease, and physical hazards affect the health of human populationsStudy large groups of people and investigate a range of possible causes and types of diseases and injuries

Disease-Causing Agents in the Environment

Infectious organismsBacteria, viruses, protozoa, and parasitic wormsTyphoid, cholera, bacterial dysentery, polio, infectious hepatitis transmittable through contaminated food and waterE. Coli is best indicator of sewage-contaminated water

Determined by fecal coliform test

Environmental Changes & Emerging Diseases

25% of disease and injury worldwide related to human-caused environmental changesCutting down forests, building dams, increasing agriculture brings humans into more contact with disease-causing agents

Increase in populationDistribution of disease-carrying organisms

Pandemic- reaches nearly entire globeExample: Swine flu

Movement of Toxicants- Through Organisms

Persistence- substance is stable and takes many years to break downBioaccumulation- buildup of persistent toxicantsBiological magnification- increase in toxicant concentrations as a toxicant passes through trophic levels of food chain

Movement of Toxicants-Through the Environment

AirWaterSoil3.5 million people in the Midwest US face slightly elevated cancer risk due to herbicides in drinking water Stockholm Convention on Persistent Organic Pollutants- protect human health and environment from persistent organic pollutants

Determining Toxicity and Health Effects

Lethal doses- depend on organism’s age, sex, health, metabolism

Human lethal doses are known through homicides and accidental poisonings

LD50- lethal to 50% of population of test animals

Smaller LD50, more toxicED50- amount to have an adverse effect

Dose-response curve- tests effects of high doses then work way down to threshold level

Maximum dose that has no measurable effect

Chemical MixturesAdditivity- exactly as expectedSynergistic- more than expectedAntagonistic- smaller than expected

The Precautionary Principle

We should not introduce new technology, practice, or material until it is demonstrated:

The risks are smallThe benefits outweigh the risksCriticisms: downplays role of science in decisions

Environmental Risks, not Natural Disasters

People need to become more aware of the environmental risks and stop building on poorly chosen landTechnologies must be updated to ensure safety

Example: nuclear plants using old technology are useless in cases of emergency

The Delaware River Issue

Industrial lands near Delaware River Fishtown, Bridesburg, Port Richmond, Kensington

Living close to the Delaware River makes you 7x more likely to live in an area with an environmental hazard than other places in the region (Mizes 2012)Also the Schuylkill: http://www.youtube.com/watch?v=Z2ge0aJwJ-o