Phase distribution of airborne chemicals is important because intake and uptake mechanisms of each phase are different. The phase distribution and concentrations are needed to determine strategies of exposure assessment, hazard control, and worker protection. However, procedures for establishing phase distribution and concentration have not been standardized. The objective of this study was to compare measurements of an airborne semivolatile pesticide (chlorpyrifos) by phase using two different procedures. Six pesticide applications in two facilities were studied and at each site, samples were collected for three time slots: T1, the first 1 or 2 hours after the commencement of application; T2, a six-hour period immediately following T1; and T3, a sixhour period after the required reentry interval (24 hours for chlorpyrifos).Two phase-separating devices were collocated at the center of each greenhouse: Semivolatile Aerosol Dichotomous Sampler (SADS) using flow-rates of 1.8 l.min-1 and 0.2 l.min-1, corresponding to a total inlet flow rate of 2.0 l.min-1 with a vapor phase flow fraction of 0.1, and electrostatic precipitator (ESP), along with a standard OVS XAD-2 tube. Chlorpyrifos in vapor and particulate form in SADS sampling train and that in vapor form in ESP sampling train were collected in OVS tubes. Chlorpyrifos in particulate form in ESP setting would have been collected on aluminum substrate. However, no chlorpyrifos in particulate form was recovered from the ESP. Overall (vapor plus particle) concentrations measured by OVS ranged 11.7 - 186.6 ug/m3 at T1 and decreased on average 77.1% and 98.9% at T2 and T3, respectively. Overall concentrations measured by SADS were 66.6%, 72.7%, and 102% of those measured by OVS on average at T1, T2, and T3, respectively. Particle fractions from the overall concentrations measured by SADS were 60.0%, 49.2%, and 13.8%, respectively, for T1, T2, and T3. SADS gives better guidance on the distribution of chlorpyrifos than does the ESP, although the accuracy of the concentration distribution cannot be verified in the absence of a standardized procedure for determining phase division.
Organic-compounds; Airborne-particles; Particulates; Particulate-dust; Humans; Men; Women; Lung; Lung-function; Lung-irritants; Chemical-composition; Chemical-properties; Work-environment; Vapors; Pesticides; Filtration; Personal-protection; Personal-protective-equipment; Agriculture; Agricultural-workers; Agricultural-chemicals; Insecticides; Exposure-levels; Risk-factors
Martin Harper, NIOSH/HELD/EAB, 1095 Willowdale Road MS-3030, Morgantown, WV 26505