Potential Uses of Biomonitoring Data: A Case Study Using the Organophosphorus Pesticides Chlorpyrifos and Malathion

Children can be exposed to pesticides from numerous residential sources such as carpet, house dust, toys and clothing from treated homes, and flea control remedies on pets. In the present studies, 48 pet dogs (24 in each of two studies) of different breeds and weights were treated with over-the-counter flea collars containing chlorpyrifos (CP), an organophosphorus insecticide. Transferable insecticide residues were quantified on cotton gloves used to rub the dogs for 5 min and on cotton tee shirts worn by a child (Study 2 only). First morning urine samples were also obtained from adults and children in both studies for metabolite (3,5,6-trichloro-2-pyridinol) quantification. Blood samples were obtained from treated dogs in Study 1 and plasma cholinesterase (ChE) activity was monitored. Transferable residues on gloves for all compounds were highest near the neck of the dogs and were lowest in areas most distant from the neck. Rubbing samples (over the collar) at two weeks post-collar application contained 447757 mg CP/glove while samples from the fur of the back contained 872 mg CP/glove. In Study 2, cotton tee shirts worn by children at 15 days post-collar application for 4 h showed CP levels of 134766 ng/g shirt. There were significant differences between adults and children in the levels of urinary metabolites with children generally having higher urinary levels of metabolites than adults (grand mean7SE; 11.671.1 and 7.970.74 ng/mg creatinine for children and adults, respectively, compared to 9.470.8 and 6.970.5 ng/mg creatinine before collar placement). Therefore, there was little evidence that the use of this flea collar contributed to enhanced CP exposure of either children or adults.

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Assessing transferable residues from intermittent exposure to flea control collars containing the organophosphate insecticide chlorpyrifos

Chambers

Boone

Davis

et al. 2007

“…Although the collection of 24-h urine samples would be preferred due to the short half-life of TCMA (USEPA, 1995), first morning voids were more practical to obtain because of the ages of the child participants (range 3-13). Furthermore, first morning voids have been used in many biological monitoring studies to evaluate the concentration of environmental chemicals in human urine (Barr and Angerer, 2006), and they have been shown to be the best predictors of weighted-average daily metabolite concentrations in the absence of a 24-h sample (Kissel et al, 2005).…”

Section: Urine Sampling Protocolmentioning

confidence: 99%

Assessing intermittent pesticide exposure from flea control collars containing the organophosphorus insecticide tetrachlorvinphos

Davis

Boone

Moran

et al. 2008

Fleas are a persistent problem for pets that require implementation of control measures. Consequently, pesticide use by homeowners for flea control is common and may increase pesticide exposure for adults and children. Fifty-five pet dogs (23 in study 1; 22 in study 2) of different breeds and weights were treated with over-the-counter flea collars containing tetrachlorvinphos (TCVP). During study 1, fur of treated dogs was monitored for transferable TCVP residues using cotton gloves to pet the dogs during 5-min rubbings post-collar application. Plasma cholinesterase (ChE) activity was also measured in treated dogs. Average amounts of TCVP transferred from the fur of the neck (rubbing over the collar) and from the back to gloves at 3 days post-collar application were 23,700 ± 2100 and 260 ± 50 mg/glove, respectively. No inhibition of plasma ChE was observed. During study 2, transferable TCVP residues to cotton gloves were monitored during 5-min rubbings post-collar application. Transferable residues were also monitored on cotton tee shirts worn by children and in the first morning urine samples obtained from adults and children. Average amounts of TCVP transferred to gloves at 5 days post-collar application from the neck (over the collar) and from the back were 22,400 ± 2900 and 80 ± 20 mg/glove, respectively. Tee shirts worn by children on days 7-11 contained 1.8 ± 0.8 mg TCVP/g shirt. No significant differences were observed between adults and children in urinary 2,4,5-trichloromandelic acid (TCMA) levels; however, all TCMA residues (adults and children) were significantly greater than pretreatment concentrations (a ¼ 0.05). The lack of ChE inhibition in dogs and the low acute toxicity level of TCVP (rat oral LD 50 of 4-5 g/kg) strongly suggest that TCVP is rapidly detoxified and excreted and therefore poses a very low toxicological risk, despite these high residues.

“…A pertinent example is chlorpyrifos and hydrolysis to TCP. The TCP can probably be absorbed through the skin at a rate equal to or greater than the parent chlorpyrifos based on structural similarity to triclopyr (Carmichael et al, 1989;Barr and Angerer, 2006). In some studies (e.g., , the background was not subtracted from daily collection of urine, also making those results conservative.…”

Section: Conservative Biases In Both Passive Dosimetry and Biomonitoringmentioning

confidence: 99%

Comparative evaluation of absorbed dose estimates derived from passive dosimetry measurements to those derived from biological monitoring: Validation of exposure monitoring methodologies

Ross

Chester²,

Driver³

et al. 2007

Passive dosimetry (PD) methods for measuring and estimating exposure to agricultural workers (i.e., persons handling agricultural chemicals and working in treated crops) have been in use since the 1950s. A large number of studies were conducted in the 1950s through 1970s to characterize exposure. Since the 1980s quantitative dermal PD methods are used in conjunction with inhalation PD methods to measure whole-body exposure. These exposure or absorbed dose estimates are then compared to ''no effect'' exposure levels for hazards identified in toxicology studies, and have become the standard for risk assessment for regulatory agencies. The PD methods used have never been validated. Validation in the context of human exposure monitoring methods means that a method has been shown to measure accurately a delivered dose in humans. The most practical alternative to isolating parts of the body for validating recovery methods is to utilize field exposure studies in which concurrent or consecutive measurements of exposure and absorbed dose have been made with PD and biomonitoring in the same cohorts of individuals. This ensures that a direct comparison can be made between the two estimates of absorbed dose, one derived from PD and the other from biomonitoring. There are several studies available (published and proprietary) employing both of these approaches. Reports involving 14 concurrent or consecutive PD-biomonitoring studies were quantitatively evaluated with 18 different methods of application or reentry scenarios for eight different active ingredients for which measured human kinetics and dermal absorption data existed. This evaluation demonstrated that the total absorbed dose estimated using PD for important handler and reentry scenarios is generally similar to the measurements for those same scenarios made using human urinary biomonitoring methods. The statistical analysis of individual worker PD:biomonitoring ratios showed them to be significantly correlated in these studies. The PD techniques currently employed yield a reproducible, standard methodology that is valid and reliably quantifies exposure.