Geoscience Reference
In-Depth Information
Fig. 4.9 Scheme showing possible sources and pathways for the occurrence of pharmaceutical
residues in the aquatic environment. Reprinted from Heberer T (
2002
). Copyright 2002 with
permission from Elsevier
infusion into the aquatic environment, those PPCPs that might have low persis-
tence can display the same exposure potential as truly persistent pollutants,
because their transformation and removal rates can be compensated by their
replacement rates. While the concentration of individual drugs in the aquatic
environment often is low (subparts per billion or subnanomolar, often referred to
as micropollutants), the presence of numerous drugs sharing a specific mode of
action could lead to significant effects through additive exposures.
Many PPCPs are used on a daily basis for very long periods, sometimes a good
portion of the user's lifetime. Although drugs are usually designed with a specific
mode of action in mind, they also can have numerous effects on nontarget, or as
yet unknown receptors, and possibly cause side effects in the target organism.
Furthermore and of equal importance, nontarget organisms can have receptors, or
receptor tissue distributions, that do not exist in the target organisms, and there-
fore, unexpected effects can result from unintentional exposure. Often PPCPs are
released to the environment in low concentrations for long periods, which in turn
may cause genetic selection of the more resistant pathogens that can reduce the
effectiveness of current medications.
Some studies (Migliore et al.
1995
) demonstrated that drugs alter the normal
post-germinative development of plants and the growth of roots, hypocotyls, and
leaves. This effect becomes more important with time, so it is more evident in
structures produced later. In other cases, drugs such as natural and synthetic
estrogens that reach the environment have been shown to produce deleterious
