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

MALATHION 181
6. POTENTIAL FOR HUMAN EXPOSURE
malathion for the 24 measured rain events ranged from 8 to 1,800 ng/m 2 ; malathion was detected in only
50% of the collected samples.
No information was found in the literature on the release of malathion to water by spillage, or on waste
water releases from formulation, manufacturing, or processing facilities. In a study of pesticides in storm
water runoff in the Sacramento River Basin in California, malathion was not detected; however, the limit
of detection for the compound was 35 ng/L (Domagalski 1996).
Malathion has been detected in surface water at 4 of the 1,623 current or former NPL sites where
malathion has been identified in some environmental medium (HazDat 2002). Malathion has been
detected in groundwater at 7 of the 1,623 current or former NPL sites where malathion has been identified
in some environmental medium (HazDat 2003).
The most recent TRI data indicate that 11 sites in the United States processed malathion in 2000 (TRI00
2002). The total of reported releases to water was 10 pounds, representing 0.26% of all environmental
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.
6.2.3 Soil
Malathion is primarily released to soils through direct deposition of spray droplets, which reach the soil
surface following aerial spraying, ground spraying, and fogging applications. These releases to soil may
occur following applications that are either made directly to soil (public health use in residential areas) or
to crops. Releases to soil may also occur as a result of wet deposition of malathion. Approximately
12.5 million pounds of malathion are applied to agricultural crops annually in the United States, with
approximately 90% of it applied through the USDA Boll Weevil Eradication Program (EPA 2000a). In
1997, over 10 millions pounds of malathion were released to areas of Texas and Alabama for this purpose
(EPA 2000a). In the four counties closest to Sequoia National Park in California’s Central Valley,
28,683 kg of malathion were applied to approximately 900,000 acres of harvested cropland in 1995, with
the peak release period occurring in March (McConnell et al. 1998). Additionally, approximately 0.5 and
3.4 million pounds are released to soil annually through applications to both agricultural sites (e.g., roads,
ditches, and near buildings) and nonagricultural sites (medfly and mosquito control, golf courses, home
and garden use), respectively (EPA 2000a).