environmental toxicant
a chemical released into the environmental that can produce adverse health effects on living organisms
acute toxicity
associated with a single exposure to a chemical, often a large dose (e.g. chemical spill)
chronic toxicity
associated with repeated exposure to small doses over a long period (e.g., eating contaminated food)
aflatoxin B1
example of chronic toxicity. a common food contaminant that can cause liver necrosis, liver failure, and death, while exposure can cause liver cancer
three major sources of toxicants
air pollution, tobacco smoke, pesticides
two categories of air pollution
- particulate matter
- gaseous air pollutants
particulate matter
a mixture of tiny particles composed of non-gaseous pollutants (solids or liquid droplets)
gaseous air pollutants
major hazards include carbon monoxide, carbon dioxide, nitrogen oxides, sulfur oxides, hydrogen sulfide, and ozone
where do pollutants come from?
both natural (volcanoes, forest fires, dust storms) and anthropogenic (man-made) sources
anthropogenic sources (man-made)
- combustion of fossil fuels for heating and power
- automobiles
- industrial processes
what is the largest contributor of human-made CO2?
coal
how do automobiles contribute to air pollutants
exhaust releases smoke, lead particles, CO, and NOx
how do industrial processes contribute to air pollutants
releases acids, solvents, chlorine, ammonia, and metals
health effects of air pollution
chemical irritation of the respiratory tract due to the combined action of particles and sulfur oxides
vulnerable populations of air pollution
young children, older adults, and those with cardiorespiratory diseases like asthma
environmental tobacco smoke
second hand smoke. combination of mainstream smoke (exhaled smoke) and sidestream smoke (smoke from the burning end of a cigarette)
health concerns of exposure to secondhand smoke
its concluded to cause lung cancer and has the same health risks as directly smoking
why are pesticides unique
they are used intentionally to kill organisms
insecticides
chemicals used to kill or prevent insects from reproducing
types of insecticides
- organochlorine insecticides (e.g., DDT)
- organophosphorus insecticides (e.g., malathion)
organochlorine insecticides (e.g., DDT) mechanism of action
- increasing the sensitivity of neurons, leading to excessive CNS stimulation, tremors, convulsions, and eventually death
organochlorine insecticides long term-problems
insect resistance, decreasing bird/fish populations, and increasing environmental concentrations (they have largely been phased out)
Organophosphorus insecticides mechanism
irreversibly inhibit acetylcholinesterase (AChE). this increases acetylcholine in nervous tissues, causing continuous neuronal firing. these are highly toxic to humans and the leading cause of poisoning in the agriculture sector
Organophosphorus insecticides effects
decreased hr, severe difficulty breathing, fecal/urinary incontinence, and blurred vision.
