paracelsus “the dose makes the poison ”. msds environmental hazards and human health chapter 17
TRANSCRIPT
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Environmental Hazards and Human Health
Chapter 17
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Risks Are Usually Expressed as Probabilities
• Risk
• Probability and possibility
• Risk Assessment
• Risk Management
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We Face Many Types of Hazards
• Five major types of hazards– Biological: pathogens– Chemical– Physical– Cultural– Lifestyle choices
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Science: Pathways for Infectious Diseases in Humans
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The World’s Seven Deadliest Infectious Diseases Kill 12.5 Million People
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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)– Resistant to most antibiotics– Symptoms of MRSA– How will it be controlled?
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Solutions: Infectious Diseases, Ways to Prevent or Reduce Their Occurrence
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Some Chemicals Can Cause Cancers, Mutations, and Birth Defects
• Toxic chemicals– Carcinogens– Mutagens– Teratogens
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Case Study: PCBs Are Everywhere—A Legacy from the Past
• Class of chlorine-containing compounds– Very stable– Nonflammable– Break down slowly in the environment– Travel long distances in the air– Fat soluble– Biomagnification– Food chains and webs
• Banned, but found everywhere
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Potential Pathways on Which Toxic Chemicals Move Through the Environment
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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
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Cont’d
• Hormonally active agents (HAAs) – Gender benders– Thyroid disrupters – Toxic chemicals
• Phthlates
• Effects on the endocrine system
• Cancer
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Science Focus: Mercury’s Toxic Effects
• Hg: teratogen and potent neurotoxin– Once airborne, persistent and not degradable– 1/3 from natural sources– 2/3 from human activities– Enters the food chain: biomagnification
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Cont’d
• 2007: Hg hotspots identified
• How are humans exposed?– Inhalation: vaporized Hg or particulates of inorganic salts– Eating fish with high levels of methylmercury
• Effects of Hg on humans
• Who is most at risk?
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Science: Cycling of Mercury in Aquatic Environments
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Solutions: Mercury Pollution
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Hormones and Hormones Mimics or Blockers
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Science Focus: Bisphenol A
• Estrogen mimic
• Found in many common products
• Laboratory findings
• Effects on human health
• Should it be banned?
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Many Factors Determine the Harmful Health Effects of a Chemical
• Toxicology
• Toxicity dependent on– Dose – Age– Genetic makeup – Multiple chemical sensitivity (MCS) – Solubility and persistence of the chemical– Biomagnification
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Cont’d
• Response– Acute effect– Chronic effect
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Science: Estimating Human Exposure to Chemicals and Measuring Their Effects
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Scientists Use Live Lab Animals and Nonanimal Tests to Estimate Toxicity
• Dose-response curve: median lethal dose (LD50) – Nonthreshold dose-response model– Threshold dose-response model
• Can the data be extrapolated to humans?
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Cont’d
• More humane methods using animals
• Replace animals with other models– Computer simulations– Tissue culture and individual animal cells– Chicken egg membranes
• What are the effects of mixtures of potentially toxic chemicals?
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Hypothetical Dose-Response Curve Showing Determination of the LD50
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Toxicity Ratings and Average Lethal Doses for Humans
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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
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Some Potentially Harmful Chemicals Found in Most Homes
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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
• 2000: global treaty to ban or phase out the dirty dozen (POPs)
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The Greatest Health Risks Come from Poverty, Gender, and Lifestyle Choices
• Risk analysis
• Greatest health risks– Poverty– Gender– Lifestyle choices
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Comparative Risk Analysis: Most Serious Ecological and Health Problems
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Global Outlook: Number of Deaths per Year in the World from Various Causes
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Comparison of Risks People Face in Terms of Shorter Average Life Span