PCBs have been widely used in dielectric fluids in capacitors and transformers, hydraulic fluids, and heat-transfer fluids. Also, they have more than 50 minor uses including plasticizers and solvents in adhesives, printing ink, sealants, moisture retardants, paints, and pesticide carriers

PCB causes cancer in laboratory animals (rats, mice, and rhesus monkeys). It is not known if it will cause cancer in humans. More study is needed to gauge its effects on the ecological food chain and on human health. When fed Coho salmon from Lake Michigan with 10 to 15 ppm PCB, mink in Wisconsin stopped reproducing or their kits died

Even normal salt concentration may be toxic if water intake is low

Selenium (Se)

Consumption of high levels in food or drinking water Presence of malnutrition, parasitic infestation, or other factors, which make people highly susceptible to selenium toxicity

From acid fruits and vegetables canned in tin cans. The acids in such foods as citrus fruits and tomato products can leach tin from the inside of the can. Then the tin is ingested with the canned food. In the digestive tract tin goes through a methylation process in which nontoxic tin is converted to methylated tin, which is toxic

Abnormalities in the hair, nails, and skin Children in a high-selenium area of Venezuela showed loss of hair, discolored skin, and chronic digestive disturbances Normally, people who have consumed large excesses of selenium excrete it as trimethyl selenide in the urine or as dimethyl selenide in the breath. The latter substance has an odor resembling garlic

Methylated tin is a neurotoxin — a toxin that attacks the central nervous system, the symptoms of which are numbness of the fingers and lips followed by a loss of speech and hearing. Eventually, the afflicted person becomes spastic, then coma and death follow

In certain regions of western United States, especially in South Dakota, Montana, Wyoming, Nebraska, Kansas, and perhaps areas in other states in the Great Plains and Rocky Mountains Also, in Canada


Selenium toxicity in people is relatively rare

Selenium toxicity may be counteracted by arsenic or copper, but such treatment should be carefully monitored

The use of tin in advanced industrial societies has increased 14-fold over the last 10 years

Tin cans are rare. Many tin cans are coated on the inside with enamel or other materials. Most cans are steel

Confirmed cases of selenium poisoning in people are rare, because (1) only traces are present in most foods, (2) foods generally come from a wide area, and (3) the metabolic processes normally convert excess selenium into harmless substances that are excreted in the urine or breath Currently, not much is known about the amount of tin in the human diet

Source: Ensminger et al.. Food and Nutrition Encyclopedia, 2nd ed., CRC Press, Boca Raton, FL, 1994.

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