Although there are numerous air pollutants, the three which will be discussed here are benzene, lead, and carbon monoxide. These are being discussed to show air pollutants may effect systems of the body other than just the respiratory tract and to show the public health success story of lead.
CO is a colorless, odorless gas produced during incomplete combustion of organic materials.
Sources
Any type of incomplete combustion produces CO but the most significant type in the outdoor environment is automobile emissions while cigarette smoking is the most significant source in the indoor environment. CO can also be emitted by combusion sources such as unvented kerosene and gas space heaters, furnaces, woodstoves, gas stoves and fireplaces.
Mechanism of Action
CO binds to the heme portion of the hemoglobin molecule just like oxygen however its affinity to 245x higher than oxygen and thus it readily displaces oxygen. As a result, the amount of oxygen carried to body tissues is reduced.
Different effects are seen at different levels. When 20-30% of the hemoglobin concentration becomes saturated with CO (called carboxy hemoglobin saturation), cardiovascular and neurobehavior changes may occur. These latter changes include headache, weakness, confusion, disorientation and dizziness. At levels of 60% carboxy hemoglobin, unconsciousness occurs and at 80%, death occurs.
Forthunately, the effects of short-term exposure are reversible. As a result, in regard to traffic exposures (i.e. sitting in heavy traffic for long periods of time) it is thought that most individuals do not achieve sufficiently high and long enough exposures to reach levels that cause neurobehavioral results. Nonethless, those individuals that work for many hours in areas of heavy traffic areas should be careful as they do receive substantial doses. High exposures do occur in unregulated environments of large cities like Mexico.
As noted above, problems can arise with improper use of various combustion sources.
Lead is a naturally occurring heavy metal. It is present in soil, water and air.
Uses of Lead
Sources of Lead in the Environment
Occupational Exposures to Lead
Children less than 7 years of age are at greatest risk of lead exposure for several reasons:
Although children from low income areas are especially vulnerable because they have diets low in calcium and iron ( theses elements suppress lead absorption), it should be noted that children of all socioeconomic levels can be affected especially as a result of eating leaded paint chips from old homes or from breathing lead-laden air from old homes that are being renovated. (Note: lead tastes sweet and this is why children eat it.)
It is thought that lead affects the CNS in young children by impairing the timed programming of cell-to-cell connection thus disrupting the normal ways the nerves of the brain are connected. It may also impair various neurotransmitter systems.
Peripheral Nervous System
Lead may destroy the myelin coating of nerves of the peripheral nervous system. Myelin covers certain nerves and helps the nerve impulse move faster. These effects on the peripheral nervous system resulted in the footdrop and wristdrop that were seen in workers with excessive occupational exposures to lead years ago.
Hematologic Effects
Lead poisoning results in anemia due to two basic effects: impairment of synthesis of heme which carries oxygen and shortened lifespan of red blood cells.
Reproductive Effects
In men, lead toxicity may be associated with infertility and chromosomal damage to sperm.
Cancer
Lead is carcinogenic in animals but evidence for carcinogenesis in humans is insufficient.
1. List the various personal exposures to benzene.
2. What are the major sources of human exposure to benzene?
3. What is hemopoiesis?
4. How does benzene cause aplastic anemia?
5. List the potential sources of exposure to carbon monoxide.
6. What are the adverse health effects of prolonged exposure to carbon monoxide?
7. List the various uses of lead today.
8. What are the primary sources of lead in the environment?
9. Why are children less than 7 years of age at greatest risk of lead exposure?
10. What is the primary way that children become exposed to lead?
11. What systems of the body does lead affect?
BACKGROUND
In 1984 a deadly cloud of methyl isocyanate killed, 2,500 people in Bhopal, India. Shortly thereafter there was a serious chemical release in West Virginia. Following these events, public interest and environmental organizations around the country accelerated demands for information on toxic chemicals being released "beyond the fence line" - outside of the facility. Consequently, the Emergency Planning and Community Right-To-Know Act (EPCRA) was enacted.
COMPONENTS OF EPCRA
EPCRA includes SERCs, (State Emergency Response Commissions), LEPCs (Local Emergency Planning Committee). TRIs, (Toxic Release Inventory), and TPQs (Threshold Planning Quantity).
What is a TRI? This component of EPCRA is essentially a database that includes information on the release, quantity, transport, treatment and disposal of potentially hazardous elements in a community. Reporting requirements are restricted to certain industries.
What is a TPQ? Part of TPI which states specific levels of chemicals present along with their physical characteristics and toxicity ratings. It essentially tells where accidents will occur, i.e., they will be most likely to occur where they are present in large quantities.
What are SERCs and LEPCs? EPCRA requires each state to designate a SERC, responsible for establishing Local Emergency Planning Committees (LEPCs) and coordinating their activities, along with developing procedures for receiving and processing public request for information collected under EPCRA, and for reviewing local emergency plans. LEPCs must develop emergency response plans in the event of chemical releases in their communities.
Define the following acronyms:
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