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

MALATHION 210
6. POTENTIAL FOR HUMAN EXPOSURE
from the tissue of aquatic organisms and is, therefore, not likely to be biomagnified in the food chain such
that it would pose human exposure threats (EPA 2000a; Howard 1991). However, bioconcentration
factor data available in the literature did not definitively show that such a concern would be unfounded.
Additional data to verify (or refute) the assumption that food chain bioaccumulation of malathion is not
an important fate process would be helpful in assessing human exposure risks from ingestion of
contaminated fish or other aquatic organisms. Data on the uptake and potential concentration of
malathion residues by plants were not found in the literature. Because malathion is utilized for home
garden purposes, there is a potential for malathion to be taken up by vegetable and other produce plants.
Although malathion is water soluble, malathion residues incorporated into the plants may be difficult to
remove through washing or other food preparation processes and the consumption of such may provide a
route for exposure. Additional data are needed on the ability of food plants to uptake malathion residues
from the soil or through aboveground plant parts that come into contact with the insecticide through direct
application.
Exposure Levels in Environmental Media. Malathion has been detected in the ambient air
(Bradman 1994; Brown et al. 1993b; Majewski et al. 1998; Wright et al. 1996), precipitation (McConnell
et al. 1998), fog (Rice 1996), surface water (Kimbrough and Litke 1996; Kucklick and Bidleman 1994;
Larson et al. 1995), groundwater (EPA 1992; Ritter 1990), soil (Krapac et al. 1995), and in/on food and
feeds (Carman et al. 1981; Lovell et al. 1996; Luke et al. 1988). Estimates of human intake of malathion
have been made for ingestion of foodstuffs (EPA 2000a; Gartrell et al. 1985, 1986; Gunderson et al.
1995a, 1995b). Limited estimates of dermal and inhalation exposure have been made for the general
population (Marty et al. 1994; Whitmore et al. 1994). Improved estimates of exposure from air, water,
and soil as well as from treated nonnatural surfaces (such as pavements, sidewalks, and playground
equipment) are needed to assess human exposure to malathion, particularly for exposures resulting from
home and garden use and public health uses. Estimates of exposure to malaoxon, the production of which
is favored in the environment under some conditions, are particularly important for assessing the human
health risks related to malathion use. Information concerning concentrations of malathion in the air,
water, and soil at the NPL hazardous waste sites known to be contaminated with malathion are needed to
assess the exposure of populations living in the vicinity of these sites.
Exposure Levels in Humans. The malathion residues malathion dicarboxylic acid (DCA) and
malathion alpha-monocarboxylic acid (MCA) may be detected in human urine samples following recent
exposure to malathion (Fenske and Leffingwell 1989; Kutz et al. 1992; MacIntosh et al. 1999a). These
compounds are specific for malathion when there is a history of exposure. Limited studies have been