Biomonitoring of persons exposed to insecticides used in residences.

Pesticides used indoors inevitably result in some unintentional and unavoidable exposures of residents. Measured dosages of residents are well below toxic levels. Exposures (microg/kg-day) are substantially less and occur over a longer time than suggested by unvalidated estimates derived from previous extreme, conservative default assumptions based solely on environmental residues. Human chlorpyrifos exposures were monitored following three different types of applications: fogger, broadcast, and crack-and-crevice. Persistence of total residue on carpet was substantially greater than the persistence of transferable residue (microg/cm(2)). Low-level (microg/kg) exposures of family members persisted for periods of weeks to a month after pesticide use. Although few children who resided with their parents in pest-protected homes have been monitored, they eliminated more biomarker than their parents on a kg body weight-day basis when absorbed dosages (microg/kg-day) were derived from spot urine specimens corrected for volume by an age-specific creatinine correction. Ultimately environmental residues may become useful elements of predictive residential exposure models, but their potential contribution to indirect exposure assessments must include careful determination of residue availability for contact transfer to clothing or skin and biological validation. When environmental data from monitoring studies reported here were used to estimate residential exposure according to Residential Exposure Assessment Standard Operating Procedures (SAP meeting, 1997), measured exposures were substantially less than assessments. Experimental and situational monitoring of exposed persons is essential for meaningful and responsible predictive resident exposure model building.

Malathion deposition, metabolite clearance, and cholinesterase status of date dusters and harvesters in California.

Date gardens in the Coachella Valley in California typically receive multiple treatments of malathion to control major insect pests. Variable amounts of malathion dust retention by skin and clothing and individual work behaviors limit the usefulness of clothing as an exposure dosimeter in date dusters and harvesters. To determine malathion absorption in workers, urine clearance of dimethyl phosphates (alkyl phosphates; AP) and malathion mono- (MCA) and di- (DCA) acids were estimated from date dusters (loaders/applicators) and harvesters (both on ground and high in trees). A series of self-administered doses of malathion were either ingested in gelatin capsules or applied to the volar surface of the forearm to guide biomonitoring. Each of the dimethyl phosphates (dimethylthio> dimethyldithio > dimethyl-) and both malathion mono- and diacids were present in urine as soon as 2-3 h of work. On a micromole basis dimethylthiophosphate and the malathion acids (MCA > DCA) were the most prominent metabolites in urine. Applicator exposures ranged from 95-210 mg equivalents per day (1-3 mg/kg-day). Harvester exposures ranged from 1-270 microg/kg-day. Mid-season Monday morning urine specimens before work contained low or unmeasurable levels of malathion acids, indicating that malathion is rapidly metabolized and cleared from the body in the urine. Saliva was not useful for biomonitoring. No inhibition of cholinesterase activity was measured in any members of two separate crews of harvesters who had previous prolonged dust exposure (1 and 2 months).

Biomonitoring and whole body cotton dosimetry to estimate potential human dermal exposure to semivolatile chemicals.

Current methods of estimating absorbed dosage (AD) of chemicals were evaluated to determine residue transfer from a carpet treated with chlorpyrifos (CP) to humans who performed a structured exercise routine. To determine the dislodgeability of residue, a California Department of Food and Agriculture (CDFA) roller was applied to a flat cotton cloth upon a treated carpet. Levels ranged from 0.06 to 0.99 microg CP/cm2. Cotton whole body dosimeters (WBD) were also used to assess residue transfer. The dosimeters retained 1.5 to 38 mg CP/person. Urine biomonitoring (3 days) for 3,5,6-trichloro-2-pyridinol (TCP) of persons who wore only swimsuits revealed a mean AD of 176 microg CP equivalents/person. The results show that the AD depends on the extent of contact transfer and dermal absorption of the residue. Default exposure assessments based upon environmental levels of chemicals and hypothetical transport pathways predict excessive exposure. The cotton WBD retains chemical residues and may be effectively used to predict dermal dose under experimental conditions.

Captan fungicide exposures of strawberry harvesters using THPI as a urinary biomarker.

Clothing affords harvesters considerable protection against the elements and can retain substantial amounts of pesticide residue from treated crops. Normal work clothing of female harvesters was supplemented with rubber latex gloves and facial scarves to determine whether those measures reduced exposure. Captan fungicide exposures in female strawberry harvesters were assessed by determining urine clearance rates of tetrahydrophalimide (THPI). Clean rubber gloves were supplied to the 41 harvesters for the 3 days of the study period in October 1995. The workers were divided into two groups consisting of either bare-handed or gloved workers, and 24-h urine specimens were collected each day. Female harvesters who worked bare-handed cleared 5.3 microg captan equivalents as THPI with a range of 0.4 to 13.8 microg/person/day. Harvesters who worked wearing rubber latex gloves cleared only 2.0 microg captan equivalents with a range of 0.9 to 4.3 microg/person/day. In this case clean rubber latex gloves reduced absorbed dose by 38%, compared to the dose absorbed by bare-handed workers. These results additionally indicate that when a pesticide is avidly retained by rubber latex gloves and not readily absorbed dermally as captan, estimates of absorbed dose based on passive dosimetry data may be less reliable than exposure estimates derived from urine biomonitoring.

Human disodium octaborate tetrahydrate exposure following carpet flea treatment is not associated with significant dermal absorption.

Disodium octaborate tetrahydrate is used for indoor flea control on carpets and furniture. Disodium octaborate tetrahydrate was applied to a 100% nylon carpet as a solution using a powered rug brush at a rate of approximately 200 micrograms/cm2 carpet. Two randomly chosen groups of volunteers (18 females, 4 males) wore either bathing suits which provided 75% or more skin exposure or whole-body, cotton dosimeters consisting of socks, union suits, and gloves. The volunteers performed a 20-minute set of Jazzercise routines. The availability of boron was demonstrated by covering portions of the carpet with a cotton dosimeter and rolling it with a weighted roller. Additionally, disodium octaborate tetrahydrate was transferred to the whole-body dosimeter. Volunteers also collected 24-hour urine specimens prior to and following the exercise period. The specimens were analyzed for total boron by inductively coupled plasma emission spectroscopy. No evidence of contact transfer and dermal absorption was obtained. The mean daily boron levels (mg/g creatinine) were 1.17, 1.33, and 1.31 for the group with exposed skin and 1.26, 1.12, and 1.26 for those who wore dosimeters which prevented contact. Daily urine boron levels were not significantly different when compared using a two sample t-test assuming equal variances (P > 0.05). Direct dermal contact with disodium octaborate tetrahydrate-treated carpet at a nominal rate of 200 micrograms/cm2 did not produce any adverse effects or change urinary boron clearance.

An evaluation of sample preparation techniques for the GC/MS analysis of urinary mercapturic acid conjugates.

Recovery rates of four different techniques for the preparation of human urine samples spiked with N-acetyl-S-benzyl-L-cysteine (BMA) were compared at three different spiking levels. At concentrations of 1,000 ppm and 1 ppm in the urine, recoveries of BMA were greatest (80-96%) using an ion pair phase transfer technique and a C18 solid-phase extraction (C18) technique while an acidic ethyl acetate extraction method yielded 67-69% recoveries and a quaternary amine solid-phase extraction technique showed poor recoveries (5-7%). At 10 ppb, quantitative recovery could only be determined for the C18 technique due to interferences from samples prepared using the other three techniques. The results indicate that the C18 sample preparation technique followed by GC/MS analysis using stable isotopically labeled internal standards provides a rapid and accurate method for quantitation of mercapturic acids at low-ppb levels in the urine.