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

MALATHION 179
6. POTENTIAL FOR HUMAN EXPOSURE
releases (Table 6-1). The TRI data should be used with caution because only certain types of facilities are
required to report. This is not an exhaustive list.
6.2.2 Water
Malathion can potentially be released to surface waters by direct application; storm runoff from sprayed
fields or urban/residential areas; atmospheric deposition following aerial application (wet deposition from
rain and fog water); waste water releases from formulation, manufacturing, or processing facilities; and
spills.
Malathion has been released to shoreline beaches and surface waters in adjacent coastal marshes on the
eastern coast of central Florida for mosquito control using aerial spraying and truck-mounted (ultra-low
volume; ULV) equipment (Clark et al. 1993).
Malathion has been detected in three rivers, which are the three largest tributaries to the Chesapeake Bay
(Foster and Lippa 1996). Malathion was collected in 6–16% of the water samples collected from the
Susquehanna, Potomac, and James Rivers in 1992–1993; mean aqueous concentrations of malathion in
the three rivers were 6, 12, and 7 ng/L, respectively. Annual loads of malathion from the three respective
tributaries to the Chesapeake Bay were determined to be 8–86, 3–25, and 3–18 kg/year, respectively
(Foster and Lippa 1996).
Malathion has been released to surface waters as a result of wet deposition following volatilization from
crop surfaces and transport through the atmosphere. Reportedly as a result of summertime agricultural
use in the Central Valley in California, and following volatilization from crop surfaces and transport
through the atmosphere, malathion was released to surface waters by wet deposition in higher elevation
regions of the Sierra Nevada Mountains; malathion was not detected in any of the dry deposition samples
(LeNoir et al. 1999). Malathion was detected in the surface waters transecting the Central Valley to the
Sierra Nevada Mountains at aqueous concentrations of 65–83 ng/L; the compound was not detected in
surface water samples collected from the two highest (of eight) elevations studied. In a study of the air,
rain, and surface water associated with a sub-estuary of the Chesapeake Bay estuarine drainage system (in
the Patuxent River watershed), which includes 57,000 km 2 of agricultural cropping areas, the total wet
deposition flux of malathion in the spring and summer of 1995 was determined to be 5,200 ng/m 2 (in the
200 mm of rain that fell during the study period; Harman-Fetcho et al. 2000). The wet deposition flux of