\ Wi]…
tomobile corrosion. In the presence
of sunlight, for example, sodium ferrocya—
nide liberates cyanide—a highly toxic chemical to humans and Wildlife [21].
Chlorinated Hyd1‘ocarbons.
A less obvious and more insidious threat
human health arises from such long-lived chemicals as the chlorinated hydro- ]
carbon pesticides such as DDT, which are transported to all parts of the globe .Î
in the air and accumulate in the environment. Early toxicity studies, which %
showed that healthy adults could ingest as much as 0.5 milligram per kilo—
gram
of body weight (mg/kg) per day of DDT (or 35 mg per person) in some
cases for as long as 21 months without any adverse effects [22], were for many lÎ
years accepted as reassurance that these pesticides posed no human health î
problems—in spite of the fact that people in various countries of the world
where measurements have been made have stored from 9—15 ppm of DDT in
their bodies [23]. As evidence of harm from DDT to both Wildlife and experi—
mental animals has begun to accumulate, however, concern has gradually
shifted from immediate toxicity to more indirect effects [24].
Infant mortality in the offspring of female rats was found to rise with in—
creasing amounts of DDT fed to the mothers and passed on to the newborn
babies in the mothers’ milk. Growth and activity in the surviving
were
also adversely affected. When the mother rats were on & protein—
decient diet, the effects of the pesticide were magnied [25]. Although the
amounts of DDT used in the experiment were higher than those to which hu—
mans are exposed, it has been found that DDT concentrates in the milk of hu—
man mothers and is passed on to their babies, too. In some Asian and African
countries, infants are nursed for two to three years. In these same countries,
}Î
DDT exposure may be particularly high and protein in the mothers’ diets
particularly low.
Other evidence is accumulating that DDT does have harmful effects on
man and animals. One of the principal physiological effects of DDT in wild
birds is its interference with reproduction by altering shell thickness. DDT
also affects the enzymatic activity of the liver in the rat, according to reports
by Michael T. Koeferl and R. E. Larson of Oregon State University [26] and
Florence K. Kinoshita of the University of Chicago [27], thus reducing one of
the body’s important defenses against ingested poisons. Chlorinated hydro—
carbons may be quite harmless while they remain stored in fat, but weight
loss which mobilizes the fat may release them to other parts of the body
where they are not so harmless. Serious health effects were found in mice af—
ter long—term exposure to DDT or dieldrin (another of the chlorinated hydrocarbons) was followed by a stress situation in which their body fat was mobi—
lized [28]. Relatively large amounts of DDT and DDE (a compound
when DDT breaks down) are transferred across the placental bar—
human mothers to their unborn children [29].
of
these experimental ndings are provocative, but not conclusive proof
of
to people. As with most environmental health problems, the thread
tar
and effect is difcult to unravel. Research in the eld is still rudimen—
Wen as DDT contamination continues to build up. Although the use of
_
158
‘
Water
-
tomobile corrosion. In the presence
of sunlight, for example, sodium ferrocya—
nide liberates cyanide—a highly toxic chemical to humans and Wildlife [21].
Chlorinated Hyd1‘ocarbons.
A less obvious and more insidious threat
human health arises from such long-lived chemicals as the chlorinated hydro- ]
carbon pesticides such as DDT, which are transported to all parts of the globe .Î
in the air and accumulate in the environment. Early toxicity studies, which %
showed that healthy adults could ingest as much as 0.5 milligram per kilo—
gram
of body weight (mg/kg) per day of DDT (or 35 mg per person) in some
cases for as long as 21 months without any adverse effects [22], were for many lÎ
years accepted as reassurance that these pesticides posed no human health î
problems—in spite of the fact that people in various countries of the world
where measurements have been made have stored from 9—15 ppm of DDT in
their bodies [23]. As evidence of harm from DDT to both Wildlife and experi—
mental animals has begun to accumulate, however, concern has gradually
shifted from immediate toxicity to more indirect effects [24].
Infant mortality in the offspring of female rats was found to rise with in—
creasing amounts of DDT fed to the mothers and passed on to the newborn
babies in the mothers’ milk. Growth and activity in the surviving
were
also adversely affected. When the mother rats were on & protein—
decient diet, the effects of the pesticide were magnied [25]. Although the
amounts of DDT used in the experiment were higher than those to which hu—
mans are exposed, it has been found that DDT concentrates in the milk of hu—
man mothers and is passed on to their babies, too. In some Asian and African
countries, infants are nursed for two to three years. In these same countries,
}Î
DDT exposure may be particularly high and protein in the mothers’ diets
particularly low.
Other evidence is accumulating that DDT does have harmful effects on
man and animals. One of the principal physiological effects of DDT in wild
birds is its interference with reproduction by altering shell thickness. DDT
also affects the enzymatic activity of the liver in the rat, according to reports
by Michael T. Koeferl and R. E. Larson of Oregon State University [26] and
Florence K. Kinoshita of the University of Chicago [27], thus reducing one of
the body’s important defenses against ingested poisons. Chlorinated hydro—
carbons may be quite harmless while they remain stored in fat, but weight
loss which mobilizes the fat may release them to other parts of the body
where they are not so harmless. Serious health effects were found in mice af—
ter long—term exposure to DDT or dieldrin (another of the chlorinated hydrocarbons) was followed by a stress situation in which their body fat was mobi—
lized [28]. Relatively large amounts of DDT and DDE (a compound
when DDT breaks down) are transferred across the placental bar—
human mothers to their unborn children [29].
of
these experimental ndings are provocative, but not conclusive proof
of
to people. As with most environmental health problems, the thread
tar
and effect is difcult to unravel. Research in the eld is still rudimen—
Wen as DDT contamination continues to build up. Although the use of
_
158
‘
Water
-