Environmental Engineering Reference
In-Depth Information
2. Insecticides and wood preservatives
A number of investigators have evaluated pesticide concentrations and
potential exposures in building environments, particularly residences. These
have included surveys associated with misapplications or alleged misappli-
cations of pesticides, contamination concerns associated with wood preser-
vatives, application-related illness complaints, nonoccupational exposures,
and exposures among farm families and farm workers.
a. Air/surface dust concentrations.
Highest air concentrations of insec-
ticides have been reported for home fogging devices. These devices
(described as bug bombs) are pressurized canisters used to control fleas,
flies, mosquitoes, ants, spiders, moths, and cockroaches. A variety of active
ingredients have been, and continue to be, used in bug bombs. The organ-
ophosphate, dichlorvos, was the most widely used insecticide in bug bombs
in the 1970s and 1980s. Because of its relatively high vapor pressure, con-
centrations within the first few hours after application were often very high
(in the range of 4 to 6 mg/m
3
), decreasing rapidly thereafter. Dichlorvos use
in pest strips has been shown to result in potentially high exposure levels
under laboratory chamber conditions simulating a typical bedroom. Con-
centrations increased from an initial 200
µ
g/m
3
to 1300
µ
g/m
3
on the 7th
day, decaying to <100
g/m
3
after 56 days. Based on the WHO acceptable
daily intake (ADI) guideline value of 4
µ
µ
g/kg body weight, dichlorvos
exposures of 200
g/m
3
would have exceeded the WHO ADI by 8 to 16
times and, in worst case situations, approximately 100 times.
In response to occupant complaints associated with retrofit sub-slab
termiticidal treatments, chlordane and heptachlor concentrations were mea-
sured in a number of Army and Air Force bases in the 1970s. Termiticides
had been, in many cases, inadvertently injected into heating ducts located
within or below the slab. Chlordane levels in approximately 14% of 500 Air
Force residences were >3.5
µ
g/m
3
. Approximately 50% of 157 private U.S.
homes investigated in another study had concentrations >5
µ
g/m
3
, an
interim guideline recommended by a committee of the National Academy
of Science. These relatively high chlordane levels were usually associated
with improper applications.
Chlordane formulations have been available as products containing 72%
chlordane:7 to 13% heptachlor, and 39.2% chlordane:19.6% heptachlor. Con-
sequently, residences contaminated with chlordane are also contaminated
with heptachlor. Because of the higher vapor pressures associated with
heptachlor, chlordane and heptachlor concentrations are often in the same
range, and, in some cases, heptachlor concentrations are higher than those
of chlordane.
In the late 1980s, USEPA conducted a large-scale study of nonoccupa-
tional pesticide exposure (NOPES) in two communities in Massachusetts
and Florida. The former was selected as a relatively high-use site; the latter,
low-use. Prevalence rates and mean concentrations for the most commonly
detected pesticides are summarized for two seasons in
Tables 4.15
and
4.16
.
µ
