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

MALATHION 192
6.3.2.4 Other Media
6. POTENTIAL FOR HUMAN EXPOSURE
Limited data were found on the degradation of malathion in or on plants. In a Canadian study conducted
to determine the persistence of malathion on strawberry plots, malathion decreased rapidly in strawberry
flowers and immature fruits (Bélanger et al. 1990). In the first year of the study, malathion decreased to
2.7% of the initial concentration within 2 days of application and was 1.5% within 7 days; in the second
study year, malathion decreased to 4.35% of the initial concentration by 3 days. Mulla et al. (1981)
reported that degradation of malathion in plants, as in soil and water, occurs mainly by means of
hydrolysis at the P-S bond; carboxylesterase-mediated hydrolysis is also of great importance.
6.4 LEVELS MONITORED OR ESTIMATED IN THE ENVIRONMENT
6.4.1 Air
In a study conducted in the fall of 1991 to determine the individual concentrations of 23 commonly used
indoor pesticides, including malathion, in indoor ambient air and dust, air samples were collected from
two rooms each of seven homes in New Jersey at two heights, 25 and 75 cm, to represent the breathing
space of a child while crawling and standing, respectively, and dust samples were collected from vacuum
cleaners (Roinestad et al. 1993). Malathion was not detected (respective detection limits of 1 and
50 ng/m 3 ) in the air or dust collected from any of the seven homes.
A study was conducted to determine the presence of 10 pesticides, including malathion, in the ambient air
of the storage rooms (5 of which were located in buildings separate from the offices) and offices of
10 commercial pest control firms in North Carolina during the summer (August) and winter (February) of
1993; an inventory taken in February 1993 indicated that 5 of the 10 companies had malathion in storage
at that time (Wright et al. 1996). Malathion was detected in 23 of the samples, at a mean concentration of
0.77 µg/m 3 and at a range of 0.02–3.57 µg/m 3 , with the maximum concentration found during the summer
in an office of a company in which the offices and storage rooms were located in one building. The
compound was detected in the air of both offices and storage rooms during both the summer and winter,
including in the air of a storage room that did not have malathion listed on the inventory.
Airborne pesticide residues were determined from air samples collected along the Mississippi River from
Louisiana to Minnesota during a 10-day period in June of 1994. Malathion, which is used minimally for