toxicological profile for malathion - Agency for Toxic Substances and ...

MALATHION 139
3. HEALTH EFFECTS
substances that are commonly found in body tissues and fluids (e.g., essential mineral nutrients such as
copper, zinc, and selenium). Biomarkers of exposure to malathion are discussed in Section 3.8.1.
Biomarkers of effect are defined as any measurable biochemical, physiologic, or other alteration within an
organism that, depending on magnitude, can be recognized as an established or potential health
impairment or disease (NAS/NRC 1989). This definition encompasses biochemical or cellular signals of
tissue dysfunction (e.g., increased liver enzyme activity or pathologic changes in female genital epithelial
cells), as well as physiologic signs of dysfunction such as increased blood pressure or decreased lung
capacity. Note that these markers are not often substance specific. They also may not be directly
adverse, but can indicate potential health impairment (e.g., DNA adducts). Biomarkers of effects caused
by malathion are discussed in Section 3.8.2.
A biomarker of susceptibility is an indicator of an inherent or acquired limitation of an organism's ability
to respond to the challenge of exposure to a specific xenobiotic substance. It can be an intrinsic genetic or
other characteristic or a preexisting disease that results in an increase in absorbed dose, a decrease in the
biologically effective dose, or a target tissue response. If biomarkers of susceptibility exist, they are
discussed in Section 3.8.2 “Populations That Are Unusually Susceptible”.
3.8.1 Biomarkers Used to Identify or Quantify Exposure to Malathion
The most specific biomarkers for exposure to malathion are the parent compound itself and metabolites in
tissues and body fluids. However, because malathion is rapidly metabolized and eliminated (see
Section 3.4), the parent compound may only be found in cases of acute exposure to considerable amounts
of the pesticide (Faragó 1967; Jadhav et al. 1992; Morgade and Barquet 1982; Vasilić et al. 1999).
Studies of the general population and occupational exposures have detected malaoxon dicarboxylic acid
(DCA), malathion monocarboxylic acid (MCA), dimethyl phosphorothioic acid (DMPT), O,O-dimethyl
phosphorodithioate (DMPDT), and O,O-dimethylphosphate (DMP) as the main metabolic products in
samples of blood and urine. In a survey of almost 7,000 people from the U.S. population conducted
during 1976–1980, about 1.1% was found to have quantifiable levels of MCA in the urine and