Drift Catching near South Woods Elementary School, Hastings, FL

Executive Summary of the Technical Report

This report presents the results of air monitoring in an agricultural area near South Woods Elementary School located adjacent to fields of Chinese cabbage in Hastings, Florida during December 2006. Monitoring was conducted for eight days, from December 6–14, and three pesticides were identified in the samples; the insecticides endosulfan and diazinon, and the herbicide trifluralin in most samples over the course of the eight-day sampling period from December 6 to 14 in 2006. The fact that pesticides were detected on most days indicates that volatilization of the pesticides is the primary source of the drift, although application-related drift may have contributed on the day(s) applications took place.

Endosulfan is an organochlorine insecticide that is applied in the US in greatest quantities to cotton, potatoes, and apples, and used in lesser amounts on a variety of vegetable and fruit crops. Residential uses of endosulfan were terminated in 2000. Endosulfan is acutely neurotoxic to both insects and mammals and a suspected endocrine disruptor. Symptoms of acute poisoning include hyperactivity, tremors, convulsions, lack of coordination, staggering, difficulty breathing, nausea/vomiting, and diarrhea. Studies have found associations between chronic exposure and delayed sexual maturity (in males) and increased incidence of birth defects of the male reproductive system. Skin irritation and brain damage have been noted among adults exposed to endosulfan occupationally. Nationwide from 1987–1997, US EPA estimated that average annual use of endosulfan was 1.38 million pounds.

Diazinon is an organophosphorus insecticide applied in the US to a wide variety of fruits, nuts, and vegetables. Diazinon is neurotoxic to both insects and mammals, inhibiting cholinesterase, an enzyme essential for the proper transmission of nerve impulses. Citing unacceptable risks to children and the environment, the US EPA banned all residential uses of diazinon effective 2004; however, agricultural use continues. Symptoms of acute poisoning range from headache, nausea and vomiting, dizziness, weakness, drowsiness, and agitation to difficulty breathing, twitching, excessive salvation and sweating, watery eyes, pinpoint pupils, confusion, inability to concentrate, and memory loss. Asthma, gestational diabetes, and certain types of cancer have been linked to chronic exposure to diazinon. Nationwide in 2001, US EPA estimated that 4-7 million pounds of diazinon were used, third behind malathion and chlorpyrifos for US organophosphorus insecticide use.

Trifluralin is a dinitroaniline herbicide used as a preemergent weed control agent to control annual grasses and broadleaf weeds on cotton, soybeans, peanuts, leafy greens, cole crops, peppers, tomatoes, and fruit trees in the US. It is also currently permitted for residential use on lawns and for use on golf courses. It is not acutely toxic, but it is listed by the EPA as a “Possible” carcinogen. Epidemiological studies of farm workers and pesticide applicators have linked trifluralin exposure to increased incidence of stomach cancer and birth defects, and animals studies show increases in urinary bladder tumors, renal pelvis carcinomas, and thyroid gland tumors. Nationwide in 2001, US EPA estimated that 12-16 million pounds of trifluralin were used.

Sample results from air monitoring in Hastings, FL are reported below and summarized in Table 2 on page 19 of the Technical Report. The data presented here should be viewed as exposure estimates that may or may not represent worst-case exposure scenarios, and do not necessarily represent the precise exposure individuals may experience. Variability in actual exposures and the effects that may be experienced by individuals are governed by breathing rates and activity levels, time spent in areas where pesticide exposure can occur, and individuals’ ability to detoxify chemicals. Inhalation may not be the sole exposure source, and total exposures from all routes (air, skin, diet) may be higher.

Of the eight samples collected (spikes and blanks excluded) between December 6th and 14th, 100% were found to be above the limit of quantitation (LOQ) of 26 nanograms (ng) of ?-endosulfan per sample (equivalent to an air concentration of 8.9 ng/m3 for a 24-hour sample at a 2.00 L/min flow rate and using a 2.00 mL solvent extraction volume). Eighty-eight percent were found to be above the LOQ of 40 ng of ?-endosulfan per sample (equivalent to an air concentration of 14 ng/m3 for a 24-hour sample at a 2.00 L/min flow rate and using a 2.00 mL solvent extraction volume). Thirty eight percent of the samples were above the 24-hour acute and sub-chronic 1-year-old child Reference Exposure Level (REL) of 340 ng/m3, calculated from the US Environmental Protection Agency’s inhalation No Observed Adverse Effect Level (NOAEL), as shown in the Calculations section of this report. A REL represents a level of concern for inhalation exposure analogous to the Reference Dose US EPA uses to assess levels of concern for dietary exposure. Twenty-five percent of the samples were above the 7-year-old REL of 500 ng/m3. The highest concentration of total endosulfan observed for a 24-hour period was 626 ng/m3 (1.8 times the 24-hour acute 1-year-old REL and 1.2 times the 7-year-old REL) on December 6, 2006, and the average concentration for the sampling period was 278 ng/m3. Endosulfan sulfate was not detected in any of the samples.

For the insecticide diazinon, 88% of the eight samples were found to be above the LOQ of 51 ng per sample (equivalent to an air concentration of 18 ng/m3 for a 24-hour sample at a 2.00 L/min flow rate and using a 2.00 mL solvent extraction volume). Sixty-three percent of the samples were above the 24-hour acute and sub-chronic 1-year-old child REL of 145 ng/m3, and 50% were above the 7-year-old REL of 220 ng/m3, calculated from the US EPA’s inhalation NOAEL, as shown in the Calculations section of this report. The highest concentration of diazinon observed for a 24-hour period was 897 ng/m3 (6.1 times the 24-hour acute 1-year-old REL and 4.1 times the 7-year-old REL) on December 12, 2006, and the average concentration for the sampling period was 311 ng/m3. The diazinon oxon degradation product was not detected in any of the samples.

For the herbicide trifluralin, 50% of the eight samples were found to be above the LOQ of 129 ng per sample (equivalent to an air concentration of 45 ng/m3 for a 24-hour sample at a 2.00 L/min flow rate and using a 2.00 mL solvent extraction volume). The highest concentration of trifluralin observed for a 24-hour period was 376 ng/m3 on December 6, 2006, and the average concentration for the sampling period was 84 ng/m3. Because this herbicide has relatively low acute toxicity to mammals, the US EPA has not determined an acute or sub-chronic NOAEL, and therefore a REL could not be calculated. Trifluralin is ranked by the US EPA as a “Possible” carcinogen, and concerns with exposure center around the carcinogenicity of the compound, not its acute or sub-chronic toxicity. For trifluralin, potential lifetime cancer risk estimates were developed for a range of hypothetical exposure scenarios to bracket the potential lifetime cancer risk from potential exposures. The lifetime cancer risk is defined as the estimated number of cancer cases above the number the medical community considers the norm for a population. Lifetime cancer risks exceeding one in one million represent risks of concern. Table 3 on page 22 shows the results for trifluralin, none of which exceed levels of concern for even the highest hypothetical exposures. See the Calculations section for full details.

Exceedances of the RELs for diazinon and endosulfan are not necessarily anticipated to cause the symptoms of acute poisoning described above; however, the REL does represent a level of concern for inhalation exposure analogous to US EPA’s Reference Dose for dietary exposure. It is unknown what exposure levels would produce the chronic effects noted above. Concentrations below the REL do not necessarily indicate that the air is “safe” to breathe. In particular, a number of recent studies evaluating the capacity of different people to metabolize toxic substances show that the variability among different people can be substantially greater than the variability assumed by US EPA in its toxicological analysis. In addition, on all but one day, all three pesticides were found in samples above detection limits. No “acceptable” levels have been established for exposures to multiple pesticides simultaneously. It is possible that additive or synergistic effects may increase the toxicity of one pesticide in the presence of others.