|·Of all chemicals in use and being produced,
only a relatively small fraction have been tested to assess for any or all
types of health effects. Aside from
lead, mercury and PCBs, there is relatively little information on the health
impact of many environmental contaminants specifically in children.
|·Frequently there is imperfect knowledge of the
mechanisms by which environmental contaminants may lead to particular health
effects. For example, although there
is modest evidence for cancer stemming from childhood exposure to pesticides,
the process remains speculative. In
part, this stems from our incomplete knowledge of many aspects of normal
developmental processes and physiological parameters.
|·Much less is understood of low-level exposures
(to organic chemicals and toxic metals) but they may predispose to chronic
illness, decrease higher brain function, especially learning, or impair fetal
and childhood development.
|·We don’t know how long after exposure at an
early age health effects might appear (i.e. the latency period), what the
effects of life-long, low-dose exposure are, as well as what effects might
occur in one generation as a result of the previous generation’s exposures
(transgenerational effects). Research
is suggesting these are all important areas of inquiry.
|·Real-world exposures to environmental
contaminants rarely mirror those seen in the controlled laboratory
experiment. We don’t have a clear
understanding of the effects of cumulative and multiple (mixed), synergistic
(combined or interactive) exposures to environmental chemicals, which we
presume every one of us undergoes.