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Human Health and Environmental Relative Risks of WNV Mosquito Control Products
RESULTS: HUMAN HEALTH RISKS; ADULTICIDES
Absolute Risks
Information from the adulticide labels found in the label review (Appendix III; Tables 1 to 5, Human Health Precautions) addresses precautions that the applicators, mixers and loaders need to take when using specific concentrated products. EPA requires certain label language depending on the hazard category of the product (Appendix III; section 1). Of the adulticide products, all but the three naled products and one permethrin product have " CAUTION " labels. The three naled products have "DANGER" labels due to their corrosive nature. The precautionary statements reflect not only the corrosivity but also the acute Toxicity category II. Fewer precautions for applicators are required on the labels of the synthetic pyrethroids due to their lower mammalian toxicity.
The EPA evaluates the risks to bystanders from short term exposure to pesticides using the MOE calculation. The toxicity factor is the lowest No Observable Adverse Effect Level (NOAEL) from the animal studies and the environmental exposure factor is modeled using a number of scenarios with a variety of assumptions, including multiple treatments. EPA's acceptable risk level is an MOE of > 100.
EPA's "Human Health Risk Assessment for Residential Post Application Exposures and Risks" for naled (7) and malathion (37) discusses exposure and risks to the US Population and children (ages 1 to 6) from ULV Mosquito uses. This assessment is for the absolute risks to residential bystanders for oral, dermal and inhalation exposure scenarios. Their conclusions for oral exposure are:
1.) Oral exposure to adults is expected to be insignificant;
2.) No oral endpoint for hand to mouth residential exposure was identified and acute dietary endpoint is for effects other than cholinesterase inhibition. Therefore EPA did not include the oral route in this scenario.
The MOE and the inputs for the MOE calculations for the other two human exposure scenarios (dermal and inhalation) for malathion are found in Table 1. Those for dermal and hand to mouth pathways for naled are found in Table 2. These routes of exposure have adequate MOEs ( > 100). For some reason, EPA did not perform an analysis of the inhalation pathway for residential bystanders; adult or children (7).
Note: The higher the MOE, the lower the risks.
Relative Risks
The objective of this report is to evaluate the relative risks of the mosquito control products. This coupled with the assumption that EPA's acceptable risk levels are not exceeded when the labels are followed, allows for the use of a surrogate for exposure (mg/A) and a modified margin of exposure calculation (modMOE). The background information supporting the relative risks analysis for all adulticides is presented in Appendix VII, Tables 1 and 2. The summary of the modMOEs for the adulticides are found in Table 3, below. In general, the mammalian modMOEs from the mosquito use of the synthetic pyrethroids is 2 to 3 orders of magnitude higher than the organophosphates.
Note: The higher the modMOE, the lower the risks.
Table 1. Short Term Risk to Residential Occupants for ULV Mosquito Malathion (37) |
Exposure pathway |
NOAEL/exposure |
US population |
Children 1-6 yrs |
Dermal
Inputs to MOE calculation |
Short term NOAEL = 50 mg/kg/day |
Adult exposure = 0.005 mg/kg/day |
Child exposure = 0.01 mg/kg/day |
MOE = NOAEL ÷ Exposure |
MOE = 10,000 |
MOE = 5,000 |
Inhalation
Inputs to MOE calculation |
Short term NOAEL = 25.8 mg/kg/day |
Adult exposure = 0.002 mg/kg/day |
Child exposure = 0.0068 mg/kg/day |
MOE = NOAEL ÷ Exposure |
MOE = 13,000 |
MOE = 3,800 |
Table 2. Short Term Risk to Residential Occupants for ULV Mosquito Naled (7) |
Exposure pathway |
NOAEL/exposure |
US population |
Children toddler |
Dermal (Ground) Inputs to MOE calculation |
Short term NOAEL = 1 mg/kg/day |
Adult exposure = 0.00069 mg/kg/day |
Child exposure = 0.00065 mg/kg/day |
MOE = NOAEL ÷ Exposure |
MOE = 1,500 |
MOE = 1,500 |
Dermal (Aerial) Inputs to MOE calculation |
Short term NOAEL = 1 mg/kg/day |
Adult exposure = 0.010 mg/kg/day |
Child exposure = 0.0097 mg/kg/day |
MOE = NOAEL ÷ Exposure |
MOE = 97 |
MOE = 100 |
Hand to mouth; object (Ground)
Inputs to MOE calculation |
Short term NOAEL = 1 mg/kg/day |
NA |
Child exposure = 0.00016 mg/kg/day |
MOE = NOAEL ÷ Exposure |
NA |
MOE = 6,100 |
Hand to mouth; object (Aerial) Inputs to MOE calculation |
Short term NOAEL = 1 mg/kg/day |
NA |
Child exposure = 0.0024 mg/kg/day |
MOE = NOAEL ÷ Exposure |
MOE = 97 |
MOE = 410 |
Hand to mouth; turf grass (Ground) Inputs to MOE calculation |
Short term NOAEL = 1 mg/kg/day |
NA |
Child exposure = 3.7 X 10 -6 mg/kg/day |
MOE = NOAEL ÷ Exposure |
NA |
MOE = 2.7 X 10 5 |
Hand to mouth; turf grass (Aerial) Inputs to MOE calculation |
Short term NOAEL = 1 mg/kg/day |
NA |
Child exposure = 5.6 X 10 -5 mg/kg/day |
MOE = NOAEL ÷ Exposure |
NA |
MOE = 18,000 |
Incidental soil ingestion (Ground) Inputs to MOE calculation |
Short term NOAEL = 1 mg/kg/day |
NA |
Child exposure = 5 X 10 -8 mg/kg/day |
MOE = NOAEL ÷ Exposure |
NA |
MOE = 2 X 10 7 |
Incidental soil (Aerial)Inputs to MOE calculation |
Short term NOAEL = 1 mg/kg/day |
NA |
Child exposure = 7.5 X 10 -7 mg/kg/day |
MOE = NOAEL ÷ Exposure |
NA |
MOE = 1.3 X 10 6 |
Inhalation Inputs to MOE calculation |
Short term NOAEL = 0.053 mg/kg/day |
Not addressed in the EPA Human Health risk assessment document for residential exposure following mosquito control |
MOE = NOAEL ÷ Exposure |
Table 3. Summary of Relative Risks (modMOE and Inputs for Calculations) for Mosquito Adulticides (from Appendix VII) |
Compound |
modExp mg/Acre |
NOAEL subchronic |
modified MOE =NOAEL / modExp |
Malathion |
272155 |
50 |
0.000184 |
Naled |
45359 |
1 |
0.000022 |
Permethrin |
3175 |
20 |
0.006299 |
Phenothrin |
1587 |
63 |
0.039698 |
Resmethrin |
3175 |
80 |
0.025197 |
NEXT: Results: Human Health Risks: Larvicides 
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