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

MALATHION 203
6. POTENTIAL FOR HUMAN EXPOSURE
in soil and dust or through direct transfer of the chemical from their skin to their mouths. Children are
also lower to the ground than adults and something that may exist at arm or hand level for an adult may
be at mouth level for a child.
Approximately 16–20% of the annual malathion use in the United States is attributed to general
agricultural use, while 59–61% is attributed to use by the USDA in eradication programs (EPA 2000a).
Approximately 0.5 million pounds of malathion are released to soil annually just through applications to
agricultural sites (e.g., roads, ditches, and near buildings); this value excludes other agricultural uses (i.e.,
crops; EPA 2000a). Children living in agricultural areas may be exposed to higher pesticide levels than
other children because of pesticides that may get tracked into the homes by household members, contact
with pesticide spray drift, or from playing in the fields near where malathion has been sprayed. Dermal
exposure is expected to be the most likely route of exposure once the pesticide has been applied, although
oral ingestion through the direct transfer caused by hand-to-mouth activity or consumption of unwashed
produce treated with malathion is also likely. Malathion is moderately to highly mobile in soil, however,
indicating that it does not readily adsorb to soil particles. Additionally, it breaks down rapidly in soils, as
does the primary oxidation product, malaoxon. Thus, the level of exposure that children will have to
malathion is dependent on the time that has passed since the application of the compound. Also, exposure
to certain levels of malathion or its residues does not mean that the compounds will be bioavailable at
those levels. No U.S. data were found on exposure or body burden measurements made on children.
Approximately 3.4 million pounds of malathion are released to soil annually through applications to
nonagricultural sites; this includes malathion use for medfly and mosquito control, golf courses, and
home and garden use (EPA 2000a). Malathion has been sprayed over large areas for public health usage,
to eradicate medflies and to control mosquito populations; approximately 8–15% of the malathion used
annually in the United States is attributed to public health use (EPA 2000a). This practice may lead to
exposure of malathion to children through dermal contact and ingestion when they play on treated soil
surfaces or in contaminated sand boxes and perform the frequent hand-to-mouth activity common in
children. To estimate exposure concentrations following repeated aerial applications of malathion to
urban/residential areas (1,500 km 2 ) of southern California for the eradication of medflies, mass deposition
data for malathion and its primary oxidation product, malaoxon, were obtained from the CDFA
Environmental Monitoring Branch (Bradman et al. 1994). Based on measured values of mass deposition,
malathion and malaoxon exposure concentrations (acute and chronic) were estimated for typical and high
or upper bound exposure levels. Estimated malathion acute and chronic exposure concentrations for a
typical exposure for the top 0.1-cm depth of soil were 14.7 and 4.9 mg/g, respectively; the corresponding