Environmental Hazards and Human Health Chapter 17

17.1

Risks Are Usually Expressed as Probabilities  Risk – probability of suffering harm from a hazard that can cause injury, disease, death, economic loss, or damage Gives likelihood of such an event

Possible…or Probably?  Possibility: it may happen  Example: It is possible that a smoker can get lung cancer.  Probability: estimate for the likelihood of an event  Example: The lifetime probability of developing lung cancer from smoking one pack of cigarettes per day is 1 in 250.

Risks Are Usually Expressed as Probabilities  Risk Assessment –using statistical methods to estimate how much harm a particular hazard can cause to human health or the environment  Risk Management – deciding whether or how to reduce a particular risk to a certain level and at what cost.

Science: Risk Assessment and Risk Management

Sensational News  Most people are not good at understanding and comparing risk… American’s worry about getting avian flu By mid-2008 had killed no one Most American’s don’t get vaccinated for the common flu Contributes to the deaths of 36,000 Americans each year

We Face Many Types of Hazards  Foods high in cholesterol or fat content  Lying out in the sun or going to a tanning salon  Living in a hurricane- prone area  How serious are the risks we face, and do the benefits of certain activities outweigh the risks?

Five major types of hazards  Biological: pathogens (bacteria, viruses, parasites, protozoa, and fungi)  Chemical: harmful chemicals in air, water, soil, and food  Physical: fire, earthquakes, volcanic eruptions, floods, and storms  Cultural: unsafe working conditions, unsafe highways, criminal assault, and poverty  Lifestyle choices: smoking, eating too much, drinking too much alcohol, and having unsafe sex

Your Turn!  Lifestyle Choices Game

Lifestyle Choices Game  Rules: Water in cup represents your BODILY FLUIDS! You are at a party where you are allowed to exchange bodily fluids… Exchange: Pour all liquid in one cup into another, then pour half back in first cup Only exchange fluids a total of three times Do NOT exchange fluids with the same person more than once

Lifestyle Choices Game  OH NO…! One person in the room is infected with influenza and does not know it… Flu test: indicator will turn the liquid in their cup bright pink if they have the virus in their fluids

Lifestyle Choices Game  Round 2 –You determine the rules…peer pressure?

17.2

Some Diseases Can Spread from One Person to Another  Nontransmissible disease – doesn’t spread from person to person Ex. Cardiovascular disease Risk increases with age…  Infectious disease – caused by pathogen that invades the body Ex. Flu, HIV, TB  Transmissible disease (contagious or communicable disease) – infectious disease that spreads from person to person

Global Outlook: Worldwide, AIDS Is the Leading Cause of Death for Ages 15–49

Major Causes of Death in the World and in the United States in 2005

Leading cause of death is cardiovascular disease…  Since 1950, death from infectious diseases have declined due to Better health care Antibiotics Vaccines  Disability-adjusted life years (DALYs) – measure of total disease burden in a population Assesses amount of ill health (includes premature death and disability) Controversial because difficult to evaluate the severity of various disabilities

Infectious Diseases Are Still Major Health Threats  Infectious diseases spread through Air Water Food Body fluids  Epidemics – large scale outbreak in a country  Pandemics – global epidemic

Science: Pathways for Infectious Diseases in Humans

The World’s Seven Deadliest Infectious Diseases Kill 12.5 Million People

Some Viral Diseases Kill Large Numbers of People  Influenza or flu virus #1 Killer Transmission  HIV #2 Killer Antiviral drugs  HBV #3 Killer Similar Transmission as HIV

Science Focus: Genetic Resistance to Antibiotics Is Increasing  Bacteria: rapid reproduction, easily spread  Over use of antibiotics  Over use of pesticides  Methicillin-resistant Staphylococcus aureus (MRSA)

Video Clip  Alien Invaders

17.3 and 17.4

Energy Pyramid Review Which level has the most energy? Which level has the most organisms? Which level has the least organisms? Which level has the least energy?

27 Solution?  dichloro-diphenyl- trichloroethane DDT

28 DDT  DDT was invented in the 1940’s and viewed as: Miracle for farmers Safe

29 DDT  Arial crop sprayers were used to spray tons of DDT on crops across the U.S

30 DDT Victim?  Scientists discovered that DDT was concentrated in the bald eagle How?  DDT affected the eagle’s ability to reproduce

Biomagnification  The increase in concentration of an element or compound, such as the pesticide DDT, that occurs in a food chain

Some Chemicals Can Cause Cancers, Mutations, and Birth Defects  Toxic chemicals – cause temporary or permanent harm or death to humans and animals Carcinogens – substances that promote cancer Mutagens – substances that cause mutations in DNA (genetic  inheritable) Teratogens – chemicals that cause harm or birth defects to a fetus or embryo

Some Chemicals May Affect Our Immune, Nervous, and Endocrine Systems  Some natural and synthetic chemicals in the environment can weaken and harm Immune system Nervous system Endocrine system

Some Chemicals May Affect Our Immune, Nervous, and Endocrine Systems  Hormonally active agents (HAAs) Gender benders – effects on sexual development and reproduction Thyroid disrupters – cause growth, weight, brain, and behavioral disorders  Phthlates (“thall-eights”) – chemicals used to soften PVC plastic used in toys, blood storage bags, and medical tubes Birth defects, liver damage, premature breast development, immune suppression, etc.

Many Factors Determine the Harmful Health Effects of a Chemical  Toxicology – study of the harmful effects of chemicals on humans and other organisms  Toxicity dependent on Dose – amount of a harmful chemical that a person has ingested, inhaled, or absorbed through the skin Age Genetic makeup Multiple chemical sensitivity (MCS) Solubility and persistence of the chemical Biomagnification

Many Factors Determine the Harmful Health Effects of a Chemical  Response Acute effect – immediate or rapid harmful reaction to an exposure Chronic effect – permanent or long-lasting consequence

Science: Estimating Human Exposure to Chemicals and Measuring Their Effects

Case Study: Protecting Children from Toxic Chemicals  Analysis of umbilical cord blood: significance 287 chemicals detected (180 carcinogenic, 217 neurological damage)  Children face a risk 10 times higher than that faced by adults…why?

Case Study: Protecting Children from Toxic Chemicals  Infants and children more susceptible to the toxic effects of chemicals than adults 1.Eat, drink, and breathe more per unit of body weight than adults 2.Put their fingers in their mouths 3.Less well-developed immune systems and body detoxification processes

Scientists Use Live Lab Animals and Nonanimal Tests to Estimate Toxicity  Dose-response curve: median lethal dose (LD50) - Dose that can kill 50% of the animals in a test population within an 18 day period

Scientists Use Live Lab Animals and Nonanimal Tests to Estimate Toxicity  Nonthreshold dose-response model – any dose causes damage  Threshold dose-response model – a threshold dosage must be reached before any detectable harm

Toxicity Ratings and Average Lethal Doses for Humans

Scientists Use Live Lab Animals and Nonanimal Tests to Estimate Toxicity  Animal Testing: Can the data be extrapolated to humans?

Scientists Use Live Lab Animals and Nonanimal Tests to Estimate Toxicity  More humane methods using animals  Replace animals with other models Computer simulations Tissue culture and individual animal cells  What are the effects of mixtures of potentially toxic chemicals?

There Are Other Ways to Estimate the Harmful Effects of Chemicals  Case reports and epidemiological studies  Limitations of epidemiological studies Too few people tested Length of time Can you link the result with the chemical? Can not be used for new hazards

Food for thought…  “Toxicologists know a great deal about a few chemicals, a little about many, and next to nothing about most.” ~Joseph V. Rodricks (risk assessment expert)  10% of 100,000 registered synthetic chemicals in commercial use have been screened for toxicity

Your Turn!  LD50 Toxicity Analysis

17.5

17-5 How Do We Perceive Risks and How Can We Avoid the Worst of Them?  Concept 17-5 We can reduce the major risks we face if we become informed, think critically about risks, and make careful choices.

Pollution Prevention and the Precautionary Principle  Those introducing a new chemical or new technology would have to follow new strategies A new product is considered harmful until it can be proved to be safe Existing chemicals and technologies that appear to cause significant harm must be removed

Some Potentially Harmful Chemicals Found in Most Homes

Comparative Risk Analysis: Most Serious Ecological and Health Problems

The Greatest Health Risks Come from Poverty, Gender, and Lifestyle Choices  Risk analysis – identifying hazards and evaluating their associated risks, ranking risks, determining options and making decisions about reducing the risk.  Greatest health risks Poverty Gender Lifestyle choices

Global Outlook: Number of Deaths per Year in the World from Various Causes

Comparison of Risks People Face in Terms of Shorter Average Life Span

Annual Deaths in the U.S. from Tobacco Use and Other Causes in 2004

Estimating Risks from Technologies Is Not Easy  System reliability = Technological reliability x Human reliability  To err is human

Most People Do Not Know How to Evaluate Risks  Fear  Degree of control  Whether a risk is catastrophic  Optimism bias  Unfair distribution of risks

Several Principles Can Help Us to Evaluate and Reduce Risk  Compare risks  Determine how much you are willing to accept  Determine the actual risk involved  Concentrate on evaluating and carefully making important lifestyle choices