Pesticide Residues in Fish - Pesticides: Evaluation of Environmental Pollution - page 366

biomagnification was DDT, which accumulated through food chains so that by the 1960s
it was shown to be interfering with the reproduction of peregrine falcons, brown pelicans,
and other predatory birds at the top of their food chains.
Organisms lower in the food chain take up and store toxins from the environment.
They are eaten up by larger predators, which are eaten, in turn, by even larger preda-
tors. The highest members of the food chain can accumulate very high levels of the
toxin (Cunningham and Saigo 1999).
13.3.3 Bioaccumulation
The process of bioaccumulation starts when pesticides applied to the agricultural land
run off during storms into rivers, streams, and eventually to the oceans. The pesticides
become part of the water column, and fish ingest the pesticides, usually through their
gills, although sometimes through their fish scales. The pesticides enter their organs and
fat tissue and are sequestered there. More and more pesticides are ingested and stored in
organs and tissues. These pesticides accumulate up the food chain as big fish eat little fish
and eventually as humans eat the fish.
Bioaccumulation is affected by how much of the pollutant gets into each organism,
the effectiveness of the elimination process of each organism, organism metabolic pro-
cesses, organism fat content, and the solubility of the pollutant. To get an accurate pic-
ture of threats to humans, this type of information for each organism within the food
chain must be obtained and added. The EPA has identified tolerance levels for pollutants
(EPA 2006). Bioaccumulation values help to determine tolerance levels in which no harm to
human health will take place. Fish advisories for pregnant women and children are more
stringent because they have different metabolic processes occurring; the same stringency
applies to people with serious illnesses.
Organochlorines, even at very low concentrations, interfere with reproduction, growth,
and development. This is one reason why there are many federal agencies that study and
regulate pesticides including the EPA, Food and Drug Administration (FDA), and National
Institutes of Health.
The FDA produces a total diet study that evaluates the pesticide residues found in fish,
meats, dairy, fruits, and vegetables as prepared (cooked) in an average US diet (Egan
2002). In 2007, 15.6% of the total fish and shellfish sample contained pesticide residues
but no fish or shellfish had levels in violation of federal standards set to protect human
health. The total diet study showed that bioaccumulation of pesticides in cooked fish is
not problematic to adults eating an average US diet, as long as no serious health issues
are apparent.
13.4 Monitoring Pesticide Residues in Fish and Fish Products
As already stated, fish accumulate chemicals from the environment because contaminants
wash into lakes and rivers and eventually reach the ocean. Some get degraded slowly and
can spread around the world. Heavy metals such as mercury, pesticide residues, and other
compounds move up the food chain from plankton to small fish and larger fish that eat
smaller ones. For this reason, nearly all fish have traces of contaminants. However, only