Chapter 15 – Environmental Hazards and Human Health

Risk Risk = Hazard x Vulnerability Hazard = anything that can cause: Injury,disease or death. Damage to personal or public property. Deterioration or destruction of the environment. Vulnerability The likelihood of being subject to a particular hazard.

Health Technically, the sum of all the factors that contribute to well-being. A working definition is: the absence of disease. Two measures of the above. Morbidity = incidence of disease in a pop. Mortality = incidence of death in a pop. Epidemiology = study of disease in a pop.

Health agencies World Health Organization (WHO) Based in Geneva. Governed by U.N. member states through the World Health Assembly. Centers for Disease Control and Prevention (CDC) The U.S. agency for protecting the health and safety of the public.

Life expectancy A universal indicator of health is human life expectancy. Essentially the statistical average life span. Varies by gender and socioeconomic level. In 1955 the average life expectancy, globally, was 48 years. Currently it is 67 years and rising. Advances in social, medical and economic well-being have added to human life expectancy.

The are disparities Between, and even within, countries there are wide differences between life expectancies depending upon social level. Glasgow, Scotland has one of the world’s greatest disparities with life expectancy for males in heavily deprived Calton standing at 54. This is 28 years less than in the affluent area of Lenzie, which is only eight kilometers away.

The risks differ with location 20% of all deaths annually are children under the age of five in the developing world. A significant cause of death to infants is dehydration due to dysentery caused by intestinal infections. The condition can be reversed with intravenous fluids but this treatment is not easily available to most people in the developing world.

Environmental hazards Four categories. Biological, physical, chemical and cultural. Biological hazards Danger from pathogens. One fourth of global deaths are due to infectious and parasitic diseases

Tuberculosis Caused by a bacterium. Mycobacterium tuberculosis. Close to one-third of the world’s people are infected. 10% will develop life-threatening symptoms. Should be controllable with antibiotics. There has been complacency about fighting the infection. Antibiotic-resistant strains have developed.

Numbers refer to incidence per 100,000 in the population.

Malaria Caused by a protozoan carried by a mosquito. Protozoan parasite = Plasmodium. Mosquito = Anopheles. A disease of the tropics. An estimated 300-350 million new cases occur annually. More than one million die every year.

Physical hazards Natural disasters. Two patterns of risk. Hurricanes, tornadoes, floods, forest fires, earthquakes, landslides and volcanic eruptions. Two patterns of risk. Hazards that strike predictably. People put themselves at risk when they build homes on floodplains, steep eroded slopes, volcanic mountain sides, coastal lowlands, etc. Much of this risk is due to poor environmental stewardship and/or population pressure. Hazards that strike randomly.

June 9, 1953

Chemical hazards. A risk associated with industrialization. Studied in the discipline of toxicology. To be covered in detail in Chapter 19. A key element in the discussion is the toxicity of a chemical. Effects can be acute, chronic or carcinogenic. Acute = immediate Chronic = long-term Carcinogenic = cancer-causing 23% of all U.S. deaths in 2003 were traced to cancer.

2005 saw a total of 559,303 U.S. deaths due to cancer U.S. cancer rates per thousand for 2005

Cultural hazards Risks to health that are a matter of choice or influenced by choices made. Obesity, excess speed, drug and alcohol abuse, occupational and recreational risk taking.

Deaths from various cultural hazards in the U.S.

Tobacco smoking is a cultural risk Leading cause of death in the U.S. 44.5 million adult smokers (20.9% of total). Half will become disabled or die because of the habit. Costs $167 billion/yr. in health care and lost production (according to the CDC). Fourth leading cause of death globally. Habit growing at a rate of 2% in the developing world. 63% of men in China are smokers. Linked to half of T.B. deaths in India.

Deaths due to smoking (ave. annual number 1997-2001

National & global response Tobacco taxes. One of the most effective means of preventing young people from taking up smoking. Warning labels. Prohibiting advertising. Banning smoking in public places. WHO Framework Convention on Tobacco Control (2003).

Indoor air pollution Smoking adds to a list of other sources of toxins in the home and workplace. More serious than second hand tobacco smoke is smoke from cooking fires in the developing world. 3 billion people worldwide rely on wood or animal dung for cooking and heating. Leads to: chronic lung diseases (such as asthma and bronchitis), lung cancer and birth-related problems.

Reducing risks One major pathway for hazards is poverty. WHO calls poverty the “world’s biggest killer.” Poverty is tied to most of the top 10 global risk factors. Poverty prevents people from accessing proper health care, nutrition, sanitation & shelter also clean water & air

DALY = Disability Adjusted Life Year DALY = Disability Adjusted Life Year. One DALY = the loss of one year of healthy life.

Priorities for improving global health Increase – Education. Especially of women. Nutrition. General level of prosperity. Requires governments that put a higher priority on these things than on military expansion and building dams, etc.

Controlling the risks due to infectious diseases. Epidemiology = “medical ecology.” One major pathway for infectious disease is unsafe food and water. Primarily a consequence of a lack of resources to build efficient waste treatment facilities. 2.6 billion people are without adequate sanitation. 1.1 billion people lack access to safe drinking water. Could also be due to a lack of education leading to poor hygiene.

Attacking the problem on many fronts in the developing world Oral hydration therapy kits. Bed nets, spraying & early treatment for malaria. WHO initiated “Roll Back Malaria” Emphasis on getting research findings into policy & practice. Develop new anti-malarial drugs. Traditional ones are becoming less effective due to resistance being developed by the parasite.

Disaster risk Subject of various U.N. initiatives. Most recently World Conference on Disaster Reduction, Kobe, Japan, January 2005. Five priorities were identified. Make risk reduction a priority. Know the risks and take action. Educate. Reduce underlying risk factors. Be better prepared at all levels.

How do we calculate the risks? Risk assessment. Study of evaluating the risks associated with a particular hazard. Risk can be calculated statistically from data that tells the number of people dying annually as a result of a particular activity. Can be expressed as loss of life expectancy. Can be expressed as probability of dying.

Number of days of lost life expectancy, from selected risks, for people in a typical developed country.

How do we use this information? Most people do not base their personal decisions on risk assessment statistics. Governments do. WHO recommends governments use risk assessment as an ideal way to form strategies to promote general health. US EPA uses risk assessment to determine the safety of chemicals.

How the EPA decides. Four steps. Hazard assessment. Which chemicals have potential to cause harm? Dose response assessment. How much does it take? Exposure assessment. How long do you need to be exposed? Risk characterization. Combine the information gathered and issue a risk assessment (ex. upper-bound, lifetime risk).

Risk management WHO 2002 World Health Report The ten leading risks are generally agreed upon. It is up to the world’s governments to act upon this information. Regulating risks requires careful analysis. Do the benefits of controlling the risk outweigh the costs? Does the risk itself provide benefits? (ex. medical x-rays) What is the public perception of the risks?

Risk perception People’s perceptions are not always consistent with the science of risk assessment. How many protests are mounted against lack of physical activity? Which, scientifically, poses the greater risk, a nuclear power plant or watching too much television?

Hazard vs. outrage Public reaction to risk is usually more a function of outrage than hazard. Hazard, in this sense, is the lethality of a risk. Outrage is has more to do with: Lack of familiarity with a technology. Extent to which the risk is voluntary. Public impression of hazards due to media coverage. Overselling of safety by advocates for a new technology. Morality. Control. Fairness.

Public concern sets government policy The EPA’s funding priorities are set largely by Congress which responds to public outrage. Risk communication should not be the media’s responsibility. A far greater part should be played by the scientific and educational communities as well as the government.

But the science is still uncertain Risk assessment is not a “perfect” way of knowing. The precautionary principle needs to be employed. With untried technologies a conservative approach is best and the proponent of an activity, rather than the public, should bear the burden of proof.

It’s our environment What we do to our environment will affect our health. A better knowledge of risk can help lead us out of unsustainable practices. Governments will adopt policies that promote a healthy environment if the citizens of a country send their leaders the right messages. Requires an informed and educated public.