Issues: Health

Healthy Milk, Healthy Baby
Chemical Pollution and Mother's Milk


The Cycle of Hazardous Chemicals


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Products of the pesticide and chemical industry that eventually end up in breast milk enter the environment in a variety of ways -- through their intended use, in accidents such as spills or explosions and through waste disposal. Once in water, soil or air, they may break down (biodegrade) or accumulate. Some chemicals are not easily broken down in nature and persist essentially unchanged for decades.

Hazardous chemicals can enter a living creature in several ways, including breathing, swallowing and absorption through the skin. Once inside, chemicals are either excreted, metabolized into less harmful compounds or stored in the body. Those that are stored are said to "persist," which is what the organochlorines that are the focus of these pages do; they seek out and attach themselves to fatty tissues. The eventual buildup of these chemicals is called bioaccumulation. Over time, the organochlorines can bioaccumulate to concentrations far greater than any concentrations in the environment.

Bioaccumulation has two phases: bioconcentration and biomagnification. If a chemical is swallowed or inhaled, and it is resistant to the detoxification mechanisms that usually eliminate chemical toxins, it remains stored in the body. The extent of storage depends partly on the chemical's tendency to enter fat or bone, where it can be stored for long periods of time. Once a chemical has been stored, the process of bioconcentration begins. Continued or repeated exposures will result in ever-increasing amounts of the chemical within that organism.

Predators higher on the food chain often eat organisms with concentrated amounts of a chemical in their bodies, thus beginning the process of biomagnification. The predator animal collects ever more concentrated levels of a chemical from all the many creatures that it eats. As that predator becomes prey, this process of increasing contamination continues up the food chain.

Eventually, the animals at the top of the food chain accumulate the highest doses. These animals include top predators such as eagles, sea lions, polar bears and humans. When mothers nurse their babies, the process of bioaccumulation extends one step further: breast-fed infants consume the fat of their mothers and get the highest doses of all.

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last revised 3.25.05

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