But the most pressing questions in the
environmental health sciences are dauntingly complex - far
too complex to yield to the narrow perspective of a single
discipline. To determine how a substance in the environment
may harm humans requires knowing where it comes from and
how it moves through natural ecosystems, how it gets into
people and how it interacts with the biological molecules
that regulate their bodies. It also requires understanding
the individual differences - in genetics, lifestyle, occupation,
other exposures - that make some people more vulnerable
than others to an environmental exposure.