Page 154 - Fundamentals of Air Pollution

122 8, Effects on Vegetation and Animals

included) consume small animals that may have ingested exotic chemicals
including pesticides, herbicides, fungicides, and antibiotics. Increasing en-
vironmental concern has pointed out the importance of the complete food
chain for the physical and mental well-being of human beings.

A. Heavy Metal Effects
One of the earliest cattle problems involved widespread poisoning of
cattle by arsenic at the turn of the century. Abnormal intake of arsenic
results in severe colic (salivation, thirst, vomiting), diarrhea, bloody feces,
and a garliclike odor on the breath; cirrhosis of the liver and spleen as well
as reproductive effects may be noted. Arsenic trioxide in the feed must be
approximately 10 mg/kg body weight for these effects to occur.
Cattle feeding on herbage containing 25-50 mg/kg (ppm wt) lead develop
excitable jerking of muscles, frothing at the mouth, grinding of teeth, and
paralysis of the larynx muscles; a "roaring" noise is caused by the paralysis
of the muscles in the throat and neck.
Symptoms of molybdenum poisoning in cattle include emaciation, diar-
rhea, anemia, stiffness, and fading of hair color. Vegetation containing
230 mg/kg of this substance affects cattle.
Mercury in fish has been found in waters in the United States and Canada.
Mercury in the waters is converted into methyl mercury by aquatic vegeta-
tion. Small fish consume such vegetation and in turn are eaten by larger
fish and eventually by humans; food with more than 0.5 ppm of mercury
(0.5 mg/kg) cannot be sold in the United States for human consumption.

B, Gaseous and Particulate Effects
Periodically, accidental emissions of a dangerous chemical affect animal
well-being. During nerve gas experimentation in a desolate area in Utah,
a high-speed airplane accidentally dropped several hundred gallons of
nerve gas. As a result of the discharge, 6200 sheep were killed. Considering
the large number of exotic chemicals being manufactured, such unfortunate
accidents may be anticipated in the future.
Fluoride emissions from industries producing phosphate fertilizers or
phosphate derivatives have caused damage to cattle throughout the world;
phosphate rock, the raw material, can contain up to 4% fluoride, part of
which is discharged to airland waters) during processing. In Polk and
Hillsborough counties of Florida, the cattle population decreased by 30,000
between 1953 and 1960 as a result of fluoride emissions. Since 1950, research
has greatly increased our knowledge of the effect of fluorides on animals;
standards and guides for diagnosing and evaluating fluorosis in cattle have
been compiled.