Chap 17Environmental Hazards

& Human Heath

RISKS AND HAZARDS

• Risk is a measure of the likelihood that you will suffer harm from a hazard.

• We can suffer from:– Biological hazards: from more than 1,400

pathogens.– Chemical hazards: in air, water, soil, and food.– Physical hazards: such as fire, earthquake, volcanic

eruption…– Cultural hazards: such as smoking, poor diet, unsafe

sex, drugs, unsafe working conditions, and poverty.

RISKS AND HAZARDS• Risk is a measure of the likelihood that you

will suffer harm from a hazard.• Distinguish between

– Possibility – Probability

• Risk assessment– Scientific process to estimate harm

• Risk management – How to reduce risk levels

Fig. 18-3, p. 419

Risk Assessment Risk Management

Hazard identification Comparative risk analysis

What is the hazard? How does it compare with other risks?

How much should it be reduced?

Risk reduction

Probability of risk

How likely is the event? Risk reduction strategy

How will the risk be reduced?

Consequences of risk Financial commitment

What is the likely damage?

How much money should be spent?

DISEASE

• Transmissible or infectious diseases– Caused by living organisms such as bacteria and

viruses– Can spread from person to person – Flu, strep throat, mono

• Nontransmissible disease– Not caused by living organisms– Can not spread from one person to another – Heart disease, asthma

Transmissible Disease

• Pathway for infectious disease in humans.

Figure 18-4

Transmissible Disease

• WHO estimates that each year the world’s seven deadliest infections kill 13.6 million people – most of them the poor in developing countries.

Figure 18-5

Vocabulary• Endemic• Mortality• Morbidity• Disease Vector• Epidemic • Pandemic• Acute• Chronic• Synergistic

Vocabulary• Endemic - native to area• Mortality• Morbidity• Disease Vector• Epidemic • Pandemic• Acute• Chronic• Synergistic

Vocabulary• Endemic - native to area• Mortality – rate of death• Morbidity• Disease Vector• Epidemic • Pandemic• Acute• Chronic• Synergistic

Vocabulary• Endemic - native to area• Mortality – rate of death• Morbidity – rate of sickness or ill effect• Disease Vector• Epidemic • Pandemic• Acute• Chronic• Synergistic

Vocabulary• Endemic - native to area• Mortality – rate of death• Morbidity – rate of sickness or ill effect• Disease Vector – transmits disease through bite• Epidemic• Pandemic• Acute• Chronic• Synergistic

Vocabulary• Endemic - native to area• Mortality – rate of death• Morbidity – rate of sickness or ill effect• Disease Vector – transmits disease through bite• Epidemic – large outbreak in one area or country• Pandemic• Acute• Chronic• Synergistic

Vocabulary• Endemic - native to area• Mortality – rate of death• Morbidity – rate of sickness or ill effect• Disease Vector – transmits disease through bite• Epidemic – large outbreak in one area or country• Pandemic – global outbreak• Acute• Chronic• Synergistic

Vocabulary• Endemic - native to area• Mortality – rate of death• Morbidity – rate of sickness or ill effect• Disease Vector – transmits disease through bite• Epidemic – large outbreak in one area or country• Pandemic – global outbreak• Acute – immediate, usually brief & severe • Chronic• Synergistic

Vocabulary• Endemic - native to area• Mortality – rate of death• Morbidity – rate of sickness or ill effect• Disease Vector – transmits disease through bite• Epidemic – large outbreak in one area or country• Pandemic – global outbreak• Acute – immediate, usually brief & severe • Chronic – long duration, usually less severe• Synergistic

Vocabulary• Endemic - native to area• Mortality – rate of death• Morbidity – rate of sickness or ill effect• Disease Vector – transmits disease through bite• Epidemic – large outbreak in one area or country• Pandemic – global outbreak• Acute – immediate, usually brief & severe • Chronic – long duration, usually less severe• Synergistic - combined effect is greater than sum

of individual effects.

Genetic Resistance to Antibiotics• Bacteria reproduce quickly: up to 16 million

offspring in 24 hours• Can quickly become resistance through natural

selection & exchanging genetic material• International travel and global trade• Over use of pesticides: increases resistance in

disease carrying pests• Over use of antibiotics in humans and livestock

– Over ½ prescribed unnecessarily

Over use of Antibiotics

• Antibiotics kill gut bacteria – good & bad• If the harmful grow back before beneficial:

– C. diff (Clostridium difficile)• Can quickly grow out of control• Virulent strains produce toxins

– Diarrhea , colitis, colon rupture, & death

• Very resistant – even to fluoroquinones• 350K hospitalizations /yr with 30K deaths in US• Fecal transplant!

Global Threat from Tuberculosis

• Tuberculosis (TB) – highly infectious.• Kills 1.7 million people per year and could kill

25 million people 2006 - 2020.• Recent increases in TB are due to:

– Lack of TB screening and control programs especially in developing countries due to cost.

– Genetic resistance to the most antibiotics.• In US Health dept investigates new cases

– Requires compliance: 6 months drug therapy

Viral Diseases – Big 3• Flu, • HIV / AIDS • hepatitis B

• infect and kill many more people each year then highly publicized West Nile and SARS viruses.

Flu

• The influenza virus is the biggest killer virus worldwide– Pigs, chickens, ducks, and geese are the major

reservoirs of flu. As they move from one species to another, they can mutate and exchange genetic material with other viruses.

Highly Potent Flu Strains

• Some strain more virulent than others – can kill 80% of infected

• Spanish Flu – 1918 - killed 50 million• Asian Flu (1957) & Hong Kong Flu(1968) –

killed 1 million each• Bird and Swine Flu more recently• New strain could kill 2 – 360 million people

– Only a matter of time

The Global HIV/AIDS Epidemic

• According to World Health Organization (WHO), in 2005 about 42 million people worldwide (1.1 million in the U.S.) were infected with HIV.

• By 2005, 25 million deaths• Each year: 3 million more deaths

HIV/AIDS Epidemic• AIDS has reduced the life

expectancy of sub-Saharan Africa from 62 to 47 – 40 years in the seven countries most severely affected by AIDS.

• Lose ½ adult pop in 10 yrs

• 15 million AIDS orphans

Projected age structure of Botswana's population in 2020…dramatically altered population pyramid

Figure 18-2

HIV/AIDS

• The virus itself is not deadly, but it cripples the immune system, leaving the body susceptible to infections such as Kaposi’s sarcoma (above).

• There is no vaccine for HIV – if you get AIDS, you will eventually die from it.

• Drugs help some infected people live longer, but only a tiny fraction can afford them.

HIV / AIDS• HIV is the second biggest killer virus worldwide.

Five major priorities to slow the spread of the disease are:– Quickly reduce the number of new infections to

prevent further spread.– Concentrate on groups in a society that are likely to

spread the disease.– Provide free HIV testing and pressure people to get

tested.– Implement educational programs.– Provide free or low-cost drugs to slow disease

progress.

Hepatitis B (HBV)• Damages liver

– Jaundice: liver can’t remove bilirubin• Kills 1 million/yr• Transmitted

– Body fluids,– Tattoes– Drug needles– Mother to child

Emerging Viral Diseases

• SARS– Outbreak in China 2002– Severe acute respiratory syndrome– Spreads quickly– Life threatening pneumonia

• West Nile– Recent increase in TX– Arial spraying for mosquitoes– Most people never even know they had it

• 2004: flu killed 36,000 west nile killed 100

Malaria – Death by Mosquito• Malaria kills

about 2 million people per year

• Majority that die are children

• Killed more than all of the wars ever fought.

Figure 18-7

Malaria – Death by Mosquito

• Cycles of Fever, chills, sweating• Weakness• Coma • Can relapse • Many survivors: permanently impaired

Malaria – Death by Mosquito

• Cases had declined during 1950’s and 60’s• Since 1970’s: come roaring back

– DDT banned– Mosquitoes: Increased resistance to pesticides

currently used– Parasites (Plasmodium): Increased resistance to

antimalarial drugs– Climate change: increasing range

• No vaccine• Prevention key

– Window screens, bed nets, clear vegetation, standing water, larva eating fish

• Spraying insides of homes with low concentrations of the pesticide DDT greatly reduces the number of malaria cases.– Under international treaty enacted in 2002, DDT

is being phased out in developing countries.• Take prophylactic medicine if traveling to

endemic areas

Malaria – Death by Mosquito

Malaria – Death by Mosquito• 40% of world’s pop live in area where malaria is

prevalent

Infectious Diseases• Majority of children in develop nations are vaccinated

– Tenanus– Measles– Diphtheria– Typhoid fever– Meningitis– Polio– Pertussis

• Cases have been increasing due to more parents not vaccinating– Access to healthcare / cost– Autism scare

• Studies have shown no correlation– Fewer vaccinated = increased risk for all

Ecological Medicine and Infectious Diseases

• infectious diseases are moving across species at increasing rates– AIDS: tribesmen eating bush meat (chimps)– Mad Cow: feeding sheep parts to cows– Lyme disease, hantavirus, SARS, swine/bird flu

• Caused by crowding, resistance, global trade, poverty, malnutrition, habitat destruction

• Ecological (conservation) medicine tracks down these connections between wildlife and humans to determine ways to slow and prevent disease spread.

Fig. 18-8, p. 424

Solutions

Infectious Diseases

Increase research on tropical diseases and vaccines

Reduce poverty

Decrease malnutrition

Improve drinking water quality

Reduce unnecessary use of antibiotics

Educate people to take all of an antibiotic prescription

Reduce antibiotic use to promote livestock growth

Careful hand washing by all medical personnel

Immunize children against major viral diseases

Oral rehydration for diarrhea victims

Global campaign to reduce HIV/AIDS

CHEMICAL HAZARDS

• Toxic chemical can cause temporary or permanent harm or death

• A hazardous chemical can harm humans or other animals because it:– Is flammable– Is explosive– An irritant– Interferes with oxygen uptake– Induce allergic reactions.

CHEMICAL HAZARDS

• A toxic chemical can cause temporary or permanent harm or death.– Mutagens are chemicals or forms of radiation that

cause or increase the frequency of mutations in DNA.

– Teratogens are chemicals that cause harm or birth defects to a fetus or embryo.

– Carcinogens are chemicals or types of radiation that can cause or promote cancer.

Effects of Chemicals on the Immune, Nervous, and Endocrine Systems

• Long-term exposure to some chemicals at low doses may disrupt the body’s systems:– Immune system:– Nervous system:– Endocrine system:

Immune System

• specialized cells and tissues that protect the body against disease and harmful substances. (arsenic, dioxins)

• Disrupting would leave body vulnerable to infection

• Arsenic & dioxins

Nervous System

• brain, spinal cord, neurons, and peripheral nerves.

• Damage can cause: behavior changes, learning disabilities, retardation, attention deficit disorder, paralysis, death

• Neurotoxins: PCBs, Mercury, arsenic, lead, some pesticides

Endocrine System• Complex network of glands that release hormones

into the bloodstream.• These hormones control metabolism, growth, sexual

production, learning ability, behavior• Chemicals can mimic our natural hormones and

impair correct function• Problems include: gender bender, thyroid, brain,

growth, behavior disorders, cancer, birth defects• Bisphenol-A (BPA) & Phthalates: leach from plastics –

found in 95% of Americans • DDT, PCBs, atrazine, aluminum, mercury

Effects onEndocrine Systems

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

Figure 18-9

A Black Day in Bhopal, India• The world’s worst industrial accident occurred in

1984 at a pesticide plant in 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– 50,000 – 60,000 permanent serious injury:

blindness, lung damage, neurological problems– Indian officials claim that

simple upgrades could have prevented the tragedy.

TOXICOLOGY: ASSESSING CHEMICAL HAZARDS

• Toxicity is a measure of how harmful a substance is – depends on:– The amount of exposure - dose – The frequency of exposure - how often– The person who is exposed - adult or child– The effectiveness of the body’s detoxification

systems - do your liver & kidneys work well– One’s genetic makeup - some people have a

higher sensitivity

TOXICOLOGY: ASSESSING CHEMICAL HAZARDS

• Typical variations in sensitivity to a toxic chemical within a population, mostly because of genetic variation.

Figure 18-10

Other Factors

• Solubility: Water or fat• Persistence: how long does it hang around in

the environment• Bioaccumulation – concentrated in tissue• Biomagnification – concentration increases as

you move up food chain (trophic levels)• Chemical interactions:

– Antagonistic – reduces harm (antioxidents)– Synergistic – increases harm (2+2=5)

TOXICOLOGY: ASSESSING CHEMICAL HAZARDS

• 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.

Protecting Children from Toxic Chemicals

• 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.

Dose is the poison• Any substance, natural or synthetic, can be

harmful if ingested in large enough dose– Water, salt

• Response: health damage from exposure– Acute– Chronic

• Should we be concerned with increasing number of chemicals all around us?– Even at trace amounts– We lack enough data to assess risk

Toxicity

• Toxicity measured by dose and response• Acute Studies megadosing rats/mice

• Threshold Level (effects can be detected)• LD50 - 50% are dead

• ED50 (sublethal effects) – 50% are effected

• ***Get a result and extrapolate the findings to humans

How Much of a Chemical Will Harm Me?

Dose Response Curves

Animal Studies

• Toxicologist– Not ethical to test toxicity on humans– Dose rats with varying levels of chemicals– Difficult to extrapolate results to humans

• Animal different species• Different body weight

– Divide LD50 by 10 for safe dose for animals– Divide by 10 again for safe dose for humans

Studies - Epidemiologists

• Retrospective- monitor people exposed in past– Bhopal

• Prospective – monitor people who might be exposed in future

• Acute – short duration• Chronic – longer period, lifespan, or until

reproductive age

Fig. 18-11, p. 431

Water pollutant levels

Air pollutant levelsSoil/dust levels

Food pesticide levels

Nutritional health

Overall health Mathematical measurements &

modeling

?

Lifestyle

Predicted level of toxicant in people

Personal habits

Genetic predisposition

MetabolismAccumulationExcretion

Lung, intestine & skin absorption rates

Total healthburden is difficult to quantify: Very complexmodel: Many variables

TOXICOLOGY: ASSESSING CHEMICAL HAZARDS

• 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.

TOXICOLOGY: ASSESSING CHEMICAL HAZARDS

• 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.

Risk Analysis

• Risk assessment - identify• Comparative risk analysis - rank• Risk management – plan to reduce risks• Risk communication – inform public and policy

makers

Cause of death Annual deaths

Poverty/malnutrition/

disease cycle

11 million (75)

Tobacco 5 million (34)

Pneumonia and flu 3.2 million (22)

Air pollution 3 million (21)

HIV/AIDS

Malaria 2 million (14)

Diarrhea 1.9 million (13)

Tuberculosis 1.7 million (12)

Car accidents 1.2 million (8)Work-related injury

& disease 1.1 million (8)

Hepatitis B 1 million (7)

Measles 800,000 (5)

3 million (21)

RISK ANALYSIS – World

Parentheses ( ) show deaths in terms of the number of fully loaded 400-passenger jumbo jets crashing every day of the year with no survivors.

RISK ANALYSIS - US

• Annual deaths in the U.S. from tobacco use and other causes in 2003.

Perceiving Risk

• Most individuals evaluate the relative risk they face based on:– Degree of control.– Fear of unknown.– Whether we voluntarily take the risk.– Whether risk is catastrophic.– Unfair distribution of risk.

• Sometimes misleading information, denial, and irrational fears can cloud judgment.

Assessing Risk

• People will do high risk things they enjoy:– Motorcycle: 1 death per 50– Driving: 1 death per 3,300

But will be terrified of low risk:Nuclear accident: 1 death in 200,000Air plane crash: 1 death in 9 million

Fig. 18-14, p. 436

Shortens average life span in the U.S. byHazard

PovertyBorn male

SmokingOverweight (35%)

Unmarried 5 yearsOverweight (15%) 2 yearsSpouse smoking 1 year

Driving 7 monthsAir pollution 5 months

Alcohol 5 monthsDrug abuse 4 months

Flu 4 monthsAIDS 3 months

Drowning 1 monthPesticides 1 month

Fire 1 monthNatural radiation 8 days

Medical X rays 5 daysOral contraceptives 5 days

Toxic waste 4 daysFlying 1 day

Hurricanes, tornadoes 1 dayLifetime near nuclear plant 10 hours

6 years6–10 years

7.5 years7–10 years

Risk Analysis: Comparison of risks people face expressed in terms of shorter average life span.

Probability of death in the US

Risk Analysis & Management

1. Recognize everything is risky2. Recognize media exaggerates risk3. Compare risks rationally: nitrites can cause

cancer, but an occasional hotdog will not be what kills you

4. Concentrate on most serious risks you can control– Eat right, exercise, don’t smoke, drive safely, wear

your seat belt, use sunscreen,

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 – “Dirty Dozen”

These include DDT, PCBs, and certain chemicals that are by-products of manufacturing processes.

In 2009, another 9 chemicals were addedPOP – Persistent Organic Pollutants