Biomonitoring is a field of scientific research which analyzes the tissues of humans or animals to detect and measure the subject's exposure to both natural and synthetic, or man-made, chemicals. Both natural and synthetic chemicals leave their impact on the body in one way or another through "markers." These markers can either be the actual chemical which remains in the body's tissues, or the by-products of its breakdown.
Biomonitoring measures what remains in the body's tissues after exposure to these chemicals. Biomonitoring does not, however, determine how the person or animal came in contact with the chemical, how they ingested it into the body, how long ago the exposure occurred, or whether the chemical exposure is actually harmful to the body. We know that natural and synthetic, harmless and toxic chemicals make their way into our soil, air and drinking water — what biomonitoring does is determine how much of it is making it into our bodies.
A biomonitoring study is generally conducted using the three following steps:
The tissues that most people think scientists would collect for a biomonitoring study are blood, urine and breast milk, but scientists also use hair, nails, fat, bone and even expelled air to conduct a biomonitoring study. Most chemicals are found in the body's tissues in extremely small quantities. Scientists measure the "body burden," or level of chemicals found in the tissues, in parts per million (ppm), parts per billion (ppb) and parts per trillion (ppt).
Certain circumstances affect "bioaccumulation" or "biomagnification," instances in which chemicals are found at much increased levels. This can occur when small animals which have been exposed to chemicals are consumed by a larger animal, and the chemical exposure is increased up the food chain. Environmental conditions such as weather can also affect the levels of certain natural chemicals released into the environment. Although biomonitoring does not provide conclusive information about how chemicals are ingested, or if they positively or adversely affect the body, it is an important component in the study of how our environment affects us physically.