Chapter 17 Human Health and Environmental Risks

Three categories of human health risks Physical Biological Chemical

Biological Risks Disease – Any impaired function of the body with a characteristic set of symptoms. Infectious diseases - those caused by infectious agents, known as pathogens. Examples: pneumonia and venereal diseases. Chronic disease – a slow steady impairment of the body. Ex. Heart disease or cancer. Acute disease - a rapid impairment of the body. Ex. Ebola

Leading Health Risks in the World The change in risk factors between low and high income countries changes over time as the given country becomes more affluent. Low Income CountryHigh Income Country

Historical Diseases Plague – cause by bacteria and transmitted by fleas Malaria – caused by bacteria and transmitted by mosquitos Tuberculosis – caused by bacteria and transmitted by people

Emergent Diseases HIV/AIDS – cause by a virus and transmitted through sexual contact, drug needles, or blood Ebola – caused by a virus and transmitted by contact Mad Cow Disease – caused by prions (protein) – transmitted by eating contaminated meat. Bird Flu – caused by a virus and transmitted by contact West Nile Virus – caused by a virus and transmitted by mosquito.

New Emergent Diseases Since the 70’s, rare diseases have been appearing throughout the world at a rate of approximately 1/year.

Chemical Risks Toxicology – is the study of chemical risks. Neurotoxins - chemicals that disrupt the nervous system. Carcinogens - chemicals that cause cancer. Teratogens - chemicals that interfere with the normal development of embryos or fetuses. Allergens - chemicals that cause allergic reactions. Endocrine disruptors - chemicals that interfere with the normal functioning of hormones in an animal’s body.

Dose-Response Studies Dose-Response Studies – expose animals or plants to different amounts of a chemical and then observe a variety of possible responses including mortality, changes in behavior, or reproduction. Acute is over a short time (1-4 days) and Chronic would be over a longer time. Concentration – amount used Dose – amount that is absorbed or consumed. Threshold – is the dose at which an effect can be detected. LD50- lethal dose that kills 50% of the individuals ED50- effective dose that causes 50% of the animals to display the harmful but nonlethal effect.

Epidemiology Epidemiology –Studying humans and animals that are exposed to chemicals and then determine whether these exposures are associated with health problems. Retrospective Studies – monitoring a group of people that have been exposed and comparing their health to a similar sized group that has not been exposed. Prospective Studies – monitoring people that might become exposed to harmful chemicals to determine if habits have an effect on future health.

Synergistic interactions- when two risks come together and cause more harm than one would. For example, the health impact of a carcinogen such as asbestos can be much higher if an individual also smokes tobacco. Problems with Epidemiological Studies

Routes of Exposure

Biomagnification Biomagnification- the increase in a chemical concentration in animal tissues as the chemical moves up the food chain. Bioaccumulation Bioaccumulation- an increased concentration of a chemical within an organism over time

Persistence Persistence- how long a chemical remains in the environment

Risk Analysis Many of our actions involve some amount of risk from environmental hazards (anything in our environment that can cause harm).

Qualitative Risk Assessment Making a judgment of the relative risks of various decisions Probability- the statistical likelihood of an event occurring and the probability of that event causing harm Perceived risk versus Actual Risk – Some people are afraid of flying because they think the plane might crash, and prefer to drive, which they perceive as much safer. Quantitative Risk Assessment The approach to conducting a quantitative risk assessment is: Risk= probability of being exposed to a hazard X probability of being harmed if exposed Assessment is always done by scientists.

Risk Acceptance Can be the most difficult part. No amount of information on the extent of the risk will overcome the conflict between those who are willing to accept some risk and those who are not. Many competing groups involved.

Risk Management Seeks to balance harm with other considerations. This is a regulatory activity that is typically carried out by local, national, and international government agencies.

Worldwide Standards of Risk Two philosophies that regulate chemicals around the world. Innocent-until-proven-guilty principle (Used by Europe)– a potential hazard should not be considered a hazard until the scientific data can definitively demonstrate that a potential hazard actually causes harm. Pro-allows “beneficial” chemicals to be introduce more quickly Con – harmful chemicals can hurt humans and wildlife for decades before sufficient evidence accumulates to confirm harm.

Worldwide Standards of Risk Precautionary Principle (Used by the USA)– when a hazard is plausible (scientific basis) but not yet certain, we should reduce or remove the hazard. Pro - prevents fewer harmful chemicals from entering the environment. Con – Beneficial chemicals could be delayed while safety is being established. This reduces financial motivation from companies to invest in new research and development.

Stockholm Convention In 2001, a group of 127 nations gathered in Stockholm, Sweden, to reach an agreement on restricting the global use of some chemicals 12 chemicals were to be banned, phased out, or reduced These include DDT, PCBs (endocrine disrupters), and certain chemicals that are by-products of manufacturing processes. European System on chemical regulation. REACH – r egister, e valuate, a uthorize, ch emical restriction – puts more responsibility on chemical companies to confirm chemicals pose no harm to people or the environment.