Environmental Health, Pollution, and Toxicology

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Chapter 8

• Environmental Health, Pollution, and Toxicology

Big Question Why Are Even Tiny Amounts of
Pollutants a Major Concern?
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Case Study Demasculinization and Feminization of
Frogs in the Environment
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Some Basics

• Can the environment make you sick?
• Disease depends on several factors, including
  physical environment, biological environment, and
  lifestyle
• Are we the only problem?
• Many natural events are hazardous

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Terminology

• Pollution refers to an unwanted change in the
  environment caused by introducing harmful
  materials or by producing harmful conditions
• Contamination implies making something unfit for
  a particular use through the introduction of
  undesirable material

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Terminology

• A toxin is a substance that is poisonous (toxic)
  to people and other living things
• Toxicology is the science that studies chemicals
  that are or could be toxic
• A carcinogen is a toxin that increases the risk
  of cancer

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• Synergism is an important concept
• It is the interaction of different substances,
  resulting in a combined effect that is greater
  than the effects of the separate substances
• Antagonism is when to substances work to
  counteract each other or cancel each other out

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• How do pollutants get into the environment?
• Point sources
• Area sources (also called non-point sources)

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• Mobile sources

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Categories of Pollutants

• Infectious Agents
• Toxic Heavy Metals
• Organic Compounds
• Thermal pollution
• Particulates
• Electromagnetic Fields
• Noise

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Heavy Metals

• These are all around us
• Heavy metals tend to accumulate over time in
  fatty body tissue. As a result, a little arsenic
  each day may eventually result in a fatal dose
• Mercury, thallium, and lead are very toxic to
  people

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Toxic Pathways

• One pathway is biomagnification
• accumulation or increase in the concentration of
  a substance in living tissue as it moves through
  a food web
• Also known as bioaccumulation

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Four Lessons about Heavy Metals

• Individuals vary in their response to the same
  dose, or amount, of a pollutant
• Pollutants may have a threshold for observation
• Some effects are reversible
• The chemical form of a pollutant, its activity,
  and its potential to cause health problems may be
  changed markedly by ecological and biological
  processes

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Lead and the Urban Environment

• Lead is one of the most common toxic metals in
  our inner-city environments

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• Lead affects nearly every system of the body
• Even small amounts may affect children
• may increase risk of attention-deficit disorder,
  aggressive behavior, and delinquency

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Organic Compounds

• Organic compounds are carbon compounds produced
  naturally by living organisms or synthetically by
  industrial processes
• Synthetic organic compounds are used in
  industrial processes, pest control,
  pharmaceuticals, and food additives
• Over 20 million chemicals!

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• Persistent organic pollutants were produced
  decades ago, when their harm to the environment
  was not known, and are now banned or restricted
• Properties
• They have a carbon-based molecular structure,
  often containing highly reactive chlorine.
• They are persistent in the environment
• They are polluting and toxic
• They are soluble in fat and therefore likely to
  accumulate in living tissue
• They can be transported by wind, water, and
  sediments for long distances

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• One example is polychlorinated biphenyls (PCBs)
• Originally used to insulate electric transformers
• The transformers deteriorated over time and
  leaked PCBs into soil and waterways
• PCBs entered the food chain and bioaccumulated in
  fish
• Fish were caught by fishermen and eaten
• PCBs may be concentrated in human fatty tissue
  and mothers milk

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• Another example is dioxin
• Dioxin is a by-product, typically of combustion
  of chemicals and waste
• Times Beach, Missouri became a dioxin ghost town
  in 1983

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• We know that dioxin is harmful to many living
  organisms
• How dioxin affects people is less certain
• The good news is that dioxin emissions have
  decreased significantly

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Thermal Pollution

• Thermal pollution occurs when heat released into
  water or air produces undesirable effects
• May be a sudden, one-time event
• Volcanic eruption
• Or a long-term, chronic problem
• Electric power plants
• Cooling Towers
• Storage Lagoons

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Particulates

• Particulates are small particles of dust
  (including soot and asbestos fibers) released
  into the atmosphere

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• Asbestoshow dangerous is it really?
• Asbestos is used as insulation and protection
  from overheating
• Excessive contact has led to asbestosis and
  cancer in some industrial workers

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• Removal of chrysolite asbestos in homes and
  public buildings is extremely expensive, and
  there is little evidence that it actually poses a
  hazard

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Noise Pollution

• Noise pollution is unwanted sound energy waves
• Loudness depends on the intensity of the energy
  carried by the sound waves
• Measured in units of decibels (dB) a
  logarithmic scale

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• Rock concerts can reach 110 dB
• Noises greater than 140 dB cause pain, and high
  levels can cause permanent hearing loss
• Loudness isnt the only problem

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General Effects of Pollutants

• Almost every part of the human body is affected

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Dose and Response

• Large amounts of any substance can be dangerous,
  while an extremely small amount can be relatively
  harmless
• Even true for water!
• Copper, chromium, and manganese are some chemical
  elements required by animals in small amounts but
  toxic in higher amounts

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Dose and Response

• Not everyone responds the same way to the same
  dose
• Who is more vulnerable? Why?
• Regulators face many challenges in trying to
  establish levels that are safe to be emitted into
  the environment
• What is being done?

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Agricultural Pesticides

• Children may suffer neurologically from
  pesticides and show increased levels of anger,
  aggression, autism, and attention deficit
  disorder.

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What about combinations of toxins?

• Two or more chemicals in the same medium (air,
  water, soil)
• Most studies only look at single chemical impacts

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Variation in Response to Pollutants

• Tolerance may vary among populations
• Pollutants can have immediate (acute) and/or
  long-term (chronic) effects.

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Risk Assessment and RiskManagement

• Risk assessment is the process of determining
  potential health effects of pollutants. It
  involves
• Identification of the hazard
• Dose-response assessment
• Exposure assessment
• Risk characterization

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• Risk management requires us to make scientific
  judgments in conjunction with technical, legal,
  political, social, and economic considerations
• Risk assessment and risk management can lead to
  arguments since the scientific opinions may be
  open to debate
• The appropriate action may be to apply the
  Precautionary Principle