Chapter 17: Environmental Hazards and Human Health

17.1 What Major Health Hazards Do We Face?

Science: Risk Assessment and Risk Management

• Risk Assessment: use of statistics to estimate harm from a hazard
  • Hazard identification
  • Probability of risk
  • Consequences of risk
• Risk Management: decisions whether and how to reduce hazards – and at what cost
  • Comparative risk analysis
  • Risk reduction
  • Risk reduction strategy
  • Financial commitment

We Face Many Types of Hazards

• There are four major types of hazards.

  1. Biological hazards come from more than 1400 pathogens (bacteria, viruses, parasites, protozoa, and fungi) that can infect humans.
  2. Chemical hazards from harmful chemicals in air, water, soil and food.
  3. Physical hazards such as fire, earthquake, volcanic eruption, flood, tornado, and hurricane.
  4. Cultural hazards such as smoking, unsafe working conditions, poor diet, drugs, drinking, driving, criminal assault, unsafe sex, and poverty.

17.2 What Types of Biological Hazards Do We Face?

• Diseases not caused by living organisms do not spread from one person to another, while those caused by living organisms such as bacteria and viruses can spread from person to person.

  1. Non-transmissible diseases tend to develop slowly, have multiple causes, are not caused by living organisms, and do not spread from one person to another. Examples are cancer, diabetes, asthma, malnutrition, and blood vessel disorders.
  2. The transmissible disease is caused by a living organism and can spread from one to another. Infectious agents/pathogens are dispersed in air, water, food, and body fluids, by some insects, and by vectors.

Some Diseases Can Spread from One Person to Another

• Infectious diseases: bacteria, viruses, and parasites that invade the body
  • passed from one person to another
  • Nontransmissible disease: the cause is not from the passage between living organisms
• Epidemic: outbreak of infectious disease
  • Pandemic: global outbreak of infectious disease

Viral Diseases Kill Large Numbers of People

• Antibiotics are not effective against viruses, so viruses can be deadly
  • Transmitted by airborne particles
• Examples→
  • HIV and hepatitis B virus: transmitted by unsafe sex; sharing needles
  • Avian flu: transmitted to humans from animals, especially from birds

Ecological Medicine

• Ecological medicine: studies the infectious disease connections between animals and humans
• Humans spread these diseases by→
  • Clearing and fragmenting forests for cities
  • Hunting wild game for food (bushmeat—may contain HIV)
  • Illegal international trade in wild species – Industrialized meat production (E. coli)

Solutions: Infectious Diseases

• Increase research on tropical diseases and vaccines
• Reduce poverty and malnutrition
• Improve drinking water quality
• Reduce unnecessary use of antibiotics
• Sharply reduce the use of antibiotics on livestock
• Immunizes children against major viral diseases
• Provide oral rehydration for diarrhea victims
• Conduct a global campaign to reduce HIV/AIDS

14.3 What Types of Chemical Hazards Do We Face?

Some Chemicals Can Cuse Cancers, Mutations, and Birth Defects

• Toxic chemical: a substance that causes temporary/permanent harm or death
  • Carcinogens: certain viruses, some types of radiation, and chemicals that cause cancer
  • Mutagens: chemicals or forms of radiation that cause or increase genetic mutations
  • Teratogens: chemicals that harm or cause birth defects – genetic changes passed on to the next generation

Some Can Affect Important Human Body Systems

• Long-term exposure to some chemicals in the environment can disrupt/weaken human body systems, especially the immune, nervous, and endocrine systems
  • Immune system
  • produces antibodies to protect from disease and harmful substances
  • Neurotoxins: substances that harm the nervous system
  • Behavioral changes, learning disabilities, attention deficit disorder, paralysis, and death

Some Chemicals Affect the Human Endocrine System

• Endocrine system: hormones released through a complex network of glands
  • Regulates/controls, growth, sexual reproduction, learning ability, and behavior
• Receptors: hormones have a molecular shape and can attach to cell walls
  • Some pesticides and synthetic chemicals (called hormone activation agents) have similar shapes and can replace hormones (hormone mimics, hormone blockers)

More Effects On the Endocrine System

• Some chemicals contain antibacterial ingredients that can reduce the effectiveness of antibiotics
  • Thyroid disrupters: cause growth, weight, brain, and behavioral disorders
  • Plastics with phthalates cause cancer, sexual irregularities, kidney/liver damage
• These endocrine system disruptions can lead to other health problems

14.4 How Can We Evaluate Chemical Hazards?

Many Factors Determine the Harmful Health Effects of Chemicals

• Toxicity: a measure of the ability of a substance to cause injury, illness, or death
  • Synthetic/natural chemicals can be harmful if ingested or inhaled in large enough quantities
• What level of chemical exposure causes harm?
  • Dose: the quantity of a harmful chemical that has been ingested, inhaled, or absorbed through the skin

Variables That Influence the Extent of Harmful Human Health Effects

• Solubility: water-soluble toxins get into water supplies, as well as the aqueous solutions that surround our body cells
  • In the body, these dissolved chemicals can penetrate the cell membranes
• Persistence: the chemical’s ability to resist being broken down into other substances
  • PCBs and DDTs break down slowly and remain in the body longer
• A dose-response curve: a plot that shows the lethal dose of the chemical
• Epidemiological studies: Compares the health of people exposed to a particular chemical with a control group

Factors Limiting the Use of Epidemiological Studies

• Too few people have been exposed to high enough dosages to see differences
• Studies are done over many years
• Isolating the effects of a single chemical is difficult because people are exposed to many chemicals during their lifetime
• Studies cannot be used on new hazards from technologies or chemicals not yet experienced

How Far Should We Go in Using Pollution Prevention and Precautionary Principles?

• Pollution prevention: do not use or release chemicals into the environment that we know or suspect can cause harm
  • Find substitutes and recycle chemicals in a closed system
• Precautionary principle: take action now to reduce suspected consequences, rather than wait for scientific results to show conclusive effects

14.5 How Do We Perceive Risks and How Can We Avoid the Worst of Them?

The Greatest Health Risks Come from Poverty, Gender, and Lifestyle Choices

• Risk analysis: risk assessment, comparative risk analysis, and risk management
• Poverty is the greatest health risk – malnutrition and increased susceptibility to non-fatal/fatal infectious diseases
  • Four greatest risks: living in poverty, being born male, smoking, and being obese
  • Premature death affected by related choices

Estimating Risks from Technologies Is Not Easy

• Reliability of a system is the probability that the system will complete a task without failing:
  • System reliability (%) = Technology Reliability (%) x Human Reliability (%)
  • High technology reliability can be achieved, but human reliability is impossible to predict
• In technology reliability, computer programs can be flawed by human design

Additional Case Study VOC Free Paint

• Until recently interior/exterior house paint contained volatile organic compounds (VOCs)
  • These toxic substances gave off fumes that lasted days/months even after the paint was totally dry
  • The fumes have harmful health effects including respiratory problems, headaches, loss of coordination, birth defects, and the liver, kidneys, and central nervous system
• As health risks became known, paint companies developed low/non-VOC paint with the same necessary attributes
  • Scrubbability, adherence of paint to the wall, one coat coverage, etc

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