Human Health Risk Assessment - Raytheon

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Human Health Risk Assessment
DRAFT
Recreational Use of Irrigation Water. In order to evaluate potential risks from use of irrigation
water for recreational purposes, we have included two additional exposure scenarios: dermal
exposure to irrigation water used to fill a child’s wading pool, and dermal exposure to irrigation
water used to operate a sprinkler. The child wading pool scenario considers children ages 1 to
6 who play in a small wading pool filled with irrigation water for 2 hours per day, 50 days per
year (about once per week), for 6 years. The sprinkler scenario considers slightly older
children, ages 2 to 11 play in the sprinkler one hour per day, 50 days per year (about once per
week) for 10 years. During each play event, we have again assumed that some incidental
ingestion of irrigation water takes place equivalent to 50 milliliters and children are exposed via
inhalation as well. RBSLs calculated for these two scenarios are well above maximum
concentrations of COPCs detected in residential irrigation wells.
These calculations also indicate that there is no threat to health under lesser exposure
scenarios such as walking barefoot across a freshly watered lawn or playing on the lawn after
watering. We also considered a swimming pool scenario in which a resident swims for 1 hour
per day, 100 days per year for 30 years. The calculated RBSLs for 1,4-dioxane, TCE and cis-
1,2-DCE are 680, 88 and 7,260 µg/L, respectively, which are all above maximum concentrations
detected to date in residential irrigation wells. Note that these RBSLs do not account for
volatilization of COPCs during filling and from the pool surface.
Surface Water Contact. The potential risk from exposure to 1,4-dioxane detected in the
surface water drainage canal along Farragut Drive North was evaluated assuming a child is
dermally exposed to the maximum detected concentration (0.009 mg/L) by wading in the canal
for 2 hours per day, one day per week, for 10 years. Under this scenario, the potential risk from
dermal contact with 1,4-dioxane is 5 x 10 -10 , which is well below any level of concern.
6.3 Potential Ecological Risks
The only COPCs detected in the surface water drainage canal along Farragut Drive North were
1,4-dioxane at a maximum concentration of 8.9 µg/L and cis-1,2-DCE at 0.68 µg/L. The
concentration of 1,4-dioxane is well below the FDEP surface water cleanup target levels of 120
µg/L, which is developed based on the protection of human health (ingestion of fish). USEPA
Region V lists an Ecological Screening Level (ESL) for 1,4-dioxane of 22,000 µg/L. 13 USEPA
Region 4 lists acute and chronic surface water toxicity screening values for cis-1,2-DCE of 606
and 24.4 µg/L, respectively. 14
Pet Exposure Scenario. Toxicity reference values for evaluating potential risks to pets from
exposure to irrigation water used for drinking water purposes are lacking. To be protective,
irrigation water concentrations should be compared to human risk standards, and in those
cases where irrigation water is found to be in excess of the FDEP drinking water standards,
pets should be supplied with an alternative potable water source (i.e. tap water).
13 http://www.epa.gov/reg5rcra/ca/ESL.pdf
14 http://www.epa.gov/region4/waste/ots/ecolbul.htm#tbl1