Neurological Impacts

Toxic airborne substances can cause neurological damage in humans. Children may be more at risk because their nervous systems are still developing. The extent of neurological damage from airborne substances is difficult to define and depends on the type of substance and the amount of exposure.

Mercury

Mercury can impair the ability to feel, see, move and taste, and can also cause numbness and tunnel vision. Long-term exposure can lead to progressively worse symptoms and ultimately personality changes, stupor and, in extreme cases, coma or death. Recent findings have described adverse cardiovascular and immune system effects at very low levels.

Lead

Short-term exposure to high levels of lead can cause vomiting, diarrhea, convulsions, coma or even death. Symptoms of long-term exposure to lower lead levels may be less noticeable but are still serious. Lead damage to the nervous system may cause lower average IQ levels within the population.

Lead is released into air through industrial emissions, smelters and refineries. With the introduction of unleaded gasoline in Canada in 1975, lead concentrations in the air have declined significantly, falling 76 percent between 1973 and 1985. Leaded gasoline in cars was banned in Canada in 1990. Since then, levels of lead in the air of most Canadian cities have dropped.

Aluminum

Abundant evidence shows that aluminum may adversely affect the nervous system in humans and animals. Historically, aluminum was considered relatively non-toxic, and healthy individuals were thought to be able to tolerate oral doses as high as 7 grams per day without harm.

Fortunately, intake of aluminum from unpolluted air is generally quite low, below 4 micrograms per day (1 microgram is 1 millionth of a gram). In industrial areas, where aluminum levels in air may be much higher, intakes can exceed 100 micrograms per day. People exposed at work may inhale between 3.5 and 7 milligrams (1 thousandth of a gram) per day.

Bioaccumulation ? the most dangerous pathway

The most dangerous route for these toxic substances to damage our neurological systems is through a process called bioaccumulation in the food chain. Many of these substances can travel long distances in the air. In turn, these substances are deposited on land or in the water where they are absorbed by organisms like plankton. The plankton is eaten by fish, which are eaten by birds, other animals and people. As animals or plants are eaten by other animals along the food chain, these pollutants continue to collect and increase in concentration. This is why toxic substances are more concentrated at the top of the food chain.