Exposure to Chlorpyrifos in Gaseous and Particulate Form in Greenhouses: A Pilot Study

Abstract

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 hr after the commencement of application; T2, a 6-hr period immediately following T1; and T3, a 6-hr period after the required re-entry interval (24 hr for chlorpyrifos).Two phase-separating devices were co-located 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 an electrostatic precipitator (ESP), along with a standard OVS XAD-2 tube. Chlorpyrifos in vapor and particulate form in a SADS sampling train and that in vapor form in an ESP sampling train were collected in OVS tubes. Chlorpyrifos in particulate form in the 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 μg/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.