Grantee Research Project Results
2004 Progress Report: Measurements and Models of Longitudinal Dietary Intake of Pyrethroid and Organophosphate Insecticides by Children
EPA Grant Number: R829396Title: Measurements and Models of Longitudinal Dietary Intake of Pyrethroid and Organophosphate Insecticides by Children
Investigators: Ryan, P. Barry
Current Investigators: Ryan, P. Barry , Kerr, William L. , Hassan, Sayed
Institution: Emory University
Current Institution: Emory University , University of Georgia
EPA Project Officer: Aja, Hayley
Project Period: February 1, 2002 through March 31, 2010
Project Period Covered by this Report: February 1, 2003 through March 31, 2004
Project Amount: $659,764
RFA: Children's Vulnerability to Toxic Substances in the Environment (2001) RFA Text | Recipients Lists
Research Category: Human Health , Children's Health
Objective:
The objectives of this research project are to: (1)measure longitudinal dietary exposure of selected insecticides for children; (2) evaluate the accuracy of children’s dietary exposure models; and (3) reduce model uncertainty. Our focus is on the validation of biomarkers in children. By measuring environmental media—air, soil, house dust, food—and modeling intake, we will make a direct comparison to biological marker concentrations.
Progress Summary:
Although the listed start date for the research project is April 2003, because of delays in novation funding reaching Emory University work did not commence on this research project until January 2004. Because the original proposal called for 1 year of protocol development, the first several months of our study were focused on this area.
Progress has been made in four areas: development of laboratory protocols, development of field protocols, development of sampling strategies, and Institutional Review Board approval.
Development of Laboratory Protocols
Extraction Procedures: Soil and House Dust. Between 1996 and 2002, our laboratory had established three methods for extracting soil and house dust samples for persistent organochlorine pesticides and organophosphate pesticides. These methods used either Soxhlet extraction or microwave-assisted extraction (MAE). MAE is a much faster procedure, taking only 30 minutes rather than the 12-18 hours required for Soxhlet. It does require the use of special containers known as Parr bombs, however, which are fairly expensive and limit the number of samples that can be extracted at once.
During the summer of 2004, we experimented with several other extraction procedures to decrease extraction time and increase sample throughput. Further, we have expanded the suite of compounds targeted for extraction and changed the focus to include pyrethrins and pyrethroids and deemphasize the organochlorine pesticides. Although the literature is replete with techniques for the extraction of these compounds, the rapid, single-extraction procedure allowing simple and inexpensive extraction of organophosphate and pyrethroid compounds is not yet available. We now are in the final stages of evaluating a single procedure that effects the extraction of these compounds from soil effectively and reproducibly using a simple 30-minute extraction on a shaker using a single solvent. Preliminary results using five pesticides (malathion, methyl parathion, diazinon, chlorpyrifos, and λ-cyhalothrin) are encouraging.
Extraction Procedures: Food. The food matrix offers significant challenges for extraction because of the highly variable nature of its makeup in different foodstuffs. We have selected three different foods as prototypes for our analyses: wheat flour, whole milk, and butter. These three materials have markedly different matrix characteristics. Wheat flour is a powder made up mostly of carbohydrates and protein. Whole milk is a liquid with a significant amount of water, but it contains suspended proteins and lipids and has a total fat content of about 4 percent. Butter is a semisolid with a very high fat content, but it contains some proteins. It is our hope that a single extraction procedure, perhaps using various cleanup methods, will prove effective in extracting pesticides quantitatively from these matrices.
Examination of the food/pesticide literature reveals that a large number of extraction procedures are extant. Many of these invoke various solvents and cleanup procedures to get reproducible results. As stated, it is our intention to reduce the number of different extraction/cleanup procedures to a minimum in an effort to standardize the method across foods, keeping in mind the difference in the food matrices from which the materials are being extracted.
We are basing our work on a method developed at the Centers for Disease Control and Prevention (CDC) for orange juice. This method uses acetonitrile as the principal extracting solvent with subsequent extraction using diethyl ether. We have produced preliminary results suggesting that we can extract spiked orange juice samples and recover all five of our targeted pesticides. To date, however, the results have not been consistent; the amount we infer from the extraction is not yet close to 100 percent of the expected, spiked amount. We have attributed some of this inconsistency to problems with our analytical instrumentation (see below).
Laboratory Analytical Protocols
The focus of our analytical protocol work has been the development of a single gas chromatography/electron capture detector (GC/ECD) method capable of quantifying organophosphate and pyrethroid pesticides at the low ppb level in toluene or another selected solvent.
Replacement of ECD. A new ECD was purchased, installed, and tested on our HP (now Agilent) 5960 II GC.
Modification of Standard Method. Our organochlorine/organophosphate pesticide method was modified to use a different temperature ramping profile to effect better resolution of pyrethroid pesticides. The modifications are being written into a standard operating procedure.
Internal Standard Response Factors. We have changed our methods to include the use of pentachloronitrobenzene (PCNB) as an internal standard. PCNB elutes just prior to diazinon under our GC conditions and column. The use of an internal standard allows greater flexibility in our analytical procedure; however, the differential response between the internal standard and the selected analyte must first be addressed. Table 1 presents these data for our trial pesticides.
Table 1. Internal Standard Response Factors for Selected Pesticides. The headings indicate diazinon, methyl parathion, malathion, chlorpyrifos, and the two isomers of λ-cyhalothrin.
Preliminary Food Results. We have obtained preliminary results for several foods—orange juice, whole milk, and wheat flour—during the past several months. We have been concerned, however, about reproducibility and recovery. Table 2 presents data indicating these concerns.
The data presented in Table 2 represent a comparison of three replicate analyses of orange juice samples spiked with 600 ppb of each pesticide. Values under the Area and Height columns represent the percentage of expected concentrations. The right-hand portion of the table compares, pairwise, the three runs.
Inspection of the table suggests the following difficulties. Methyl parathion is recovered in excess of what is expected. This compound has been difficult for us. The chromatographic peaks tail sharply, and we suspect degradation. This occurs both in standards and in samples. We are evaluating several solutions to this problem.
Recoveries of the other species are lower than expected (NB expected recovery of the two l-cyhalothrin isomers is expected to be 50% rather than 100.) Although this is a concern, it is less of a problem than the methyl parathion overprediction.
Reproducibility is somewhat problematic. Generally, the runs show reproducibility near what might be expected on trace pesticide analysis; however, the diazinon values are quite close for two of the runs, whereas the third is well off from the others. Similar statements can be made regarding l-cyhalothrin, although to a lesser degree.
We are continuing to modify and update our methods to ensure a reproducible analysis with effective recoveries.
Table 2. Comparison of Three Replicate Analyses of Orange Juice Samples Spiked With 600 ppb of Each Pesticide. Values under Area and Height columns represent percentage of expected concentrations observed. The right-hand portion of the table compares, pairwise, the three runs.
Preliminary Soil Results. Our soil extraction experiments are underway. We are performing direct comparisons of Soxhlet extractions with various other procedures; however, final analysis awaits an approved and stable GC/ECD method.
Development of Field Protocols
Field protocols have been developed for house dust, soil, and air monitoring. These protocols are based on those implemented in the National Human Exposure Assessment Survey (NHEXAS)-Maryland investigation and have been tested and modified slightly to account for changes in laboratory analytical procedures since the NHEXAS-Maryland investigation.
House Dust . House dust samples will be collected using the HVS3 high-volume dust sampler. This sampling apparatus is a refitted vacuum sampler using an inlet/flow/cyclone design that delivers particles larger than 5 µm in diameter to a collection bottle located on the front. The collected dust samples are first passed through a coarse (2 mm) screen designed to remove animal fur, etc., and then a small screen (250 µm) to retain the dust that is most likely to adhere to skin or be inhaled. Analysis is completed after extracting with the solvent. Vacuuming a 1 m2 area of carpeting is usually sufficient to give a 2-5 g final sample of dust. A detailed protocol is in final editing.
Soil . Soil samples are taken from various locations around the participant’s yard and at the dripline near the foundation. A total of 24 “plugs” of about 15 cm3 each are composited into a single sample for later analysis. A total of 500-1,000 g of soil are taken. After returning to the laboratory, the soil samples are allowed to air dry prior to passing the entire sample through a coarse (2 mm) screen to remove rocks, pebbles, sticks, and other organic debris. A 150 g aliquot of this soil is stored for later analysis. A detailed protocol is in final editing.
Air . Air samples are taken by drawing air through a particle filter and subsequently through a precleaned polyurethane foam (PUF) plug. Airborne pesticides are collected on the PUF plug. The flow rate for the sampling apparatus is 4 liters per minute, giving a total sample of 5.76 m3 assuming a 24 hour sample. Flows are measured at the beginning and end of sampling with the average flow used to determine volume. PUF samplers are brought back to the laboratory and stored in closed jars in a freezer prior to extraction and analysis.
Development of Sampling Strategies
Sampling strategies are often problematic in exposure assessment field investigations. Our original plans called for a statistically representative sample of participants to be drawn. The relatively small size of our study, however, may call the need for and utility of this plan into question. Currently, we are considering alternative strategies prior to final selection.
Sample Size Analyses . Laboratory throughput in both our own facilities and with our collaborating group at the CDC limits the total number of individuals that we can sample. Further, since this is a longitudinal investigation requiring us to obtain three time-separated samples from each individual, our sample size is limited further. Preliminary budgetary analysis suggests that, assuming at least three measurements per individual spaced several months apart, we have sufficient resources to collect samples from 30-70 individuals.
Statistical Versus Convenience Sampling . Currently, we are exploring options for sample collection. Because the sample size likely is to be quite small and the burden placed on the individuals substantial, we are considering choosing a convenience sample versus a sample statistically representative of some population. We are focusing initially on a convenience-based strategy to minimize the number of nondetected samples. A comprehensive literature search is underway to identify geographic and questionnaire-based screening methods that have been effective in previous insecticide exposure studies. We anticipate that the final sampling strategy will involve an initial geographic screening (resolution to be determined) followed by an insecticide use screening questionnaire and home inspection. We anticipate spending significant effort on developing the screening questionnaire because recent studies by other researchers (Sexton, et al., 2003) have shown existing questionnaires to be ineffective in predicting residential organophosphate concentrations. Because we expect the pyrethrin/pyrethroid compounds to be less stable than organophosphates in residential exposure media under most conditions, we expect the predictive power of existing questionnaires to be low for our target analytes.
Location Strategies . We are focusing on the interface between the growing Atlanta metropolitan area and the formerly rural counties that are historically the sites of robust agricultural activities. We are compiling historical land-use data for these counties from the University of Georgia’s Natural Resources Spatial Analysis Laboratory (http://narsal.ecology.uga.edu/glut.html Exit ) and other sources. We also recently completed a review of potential point sources in the region using the U.S. Environmental Protection Agency’s Envirofacts Data Warehouse multisystem query function.
Institutional Review Board Approval
Dr. Riederer has begun discussions with the Emory Human Investigations Committee (HIC), our Institutional Review Board, in preparation for our submission. Although our work will require only environmental samples and urine samples and should be subject to expedited review, we are working closely with the HIC because our primary focus is on a sensitive population, namely children. Because we are projecting piloting field data collection in the first quarter of 2005 (see below), we will need final approval of our protocol by fourth quarter 2004.
References:
Sexton K, Adgate JL, Eberly LE, Clayton CA, Whitmore RW, Pellizzari ED, Lioy PJ, Quackenboss JJ. Predicting children’s short-term exposure to pesticides: results of a questionnaire screening approach. Environmental Health Perspectives 2003;111(1):123-128.
Future Activities:
We will:
- Continue development of extraction protocols for soil and house dust: September-December 2004.
- Continue development of extraction procedures for food: September 2004-March 2005.
- Develop extraction procedures for airborne pesticides: November-December 2004.
- Conduct field trials of staff members’ homes: November-December 2004.
- Perform laboratory analysis of field trials: December 2004-January 2005.
- Conduct field study participant selection: November-December 2004.
- Conduct field pilot with real participants: January-February 2005.
- Evaluate field protocols: March 2005.
- Begin first cycle of field data collection: April 2005.
Journal Articles:
No journal articles submitted with this report: View all 14 publications for this projectSupplemental Keywords:
indoor air, soil, food, biological media, exposure, bioavailability, metabolism, diet, pesticides, pesticide metabolites, environmental chemistry, analytical methods, longitudinal surveys, southeast,, RFA, Scientific Discipline, Health, PHYSICAL ASPECTS, Toxics, Air, Health Risk Assessment, air toxics, pesticides, Risk Assessments, Susceptibility/Sensitive Population/Genetic Susceptibility, Physical Processes, Biochemistry, Children's Health, genetic susceptability, pesticide exposure, rural communities, urban air, sensitive populations, monitoring, adolescents, organophosphates, multi-pathway study, exposure, age-related differences, dermal contact, children, longitudinal study, human exposure, gender-related variability, pesticide residues, insecticides, environmental toxicant, neurotixics, dust , biological markers, dietary exposure, human health risk, agricultural community, organophosphate pesticides, exposure assessmentProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.
Project Research Results
- Final Report
- 2009 Progress Report
- 2008
- 2007 Progress Report
- 2006 Progress Report
- 2005 Progress Report
- 2003
- 2002
- Original Abstract
4 journal articles for this project