TCA in groundwater Anne Karvonen Juha Villman Mikko Pohjola

Introduction Focus: 1,1,1-Trichloroethane in Groundwater Scope: Santa Clara Valley (Silicon Valley) in California TCA hazard to humans Other exposures, besides exposure to TCA in groundwater taken from wells, excluded All data from an article with abovementioned title, written in the 80's

Identification of hazard Fate in body TCA is absorbed efficiently (~100%) from the gastrointestinal tract and approximately with 30% efficiency from the lungs Chemical is rapidly distributed to all tissues via bloodstream Inhaled (uptaken) and ingested chemical assumed to behave/affect similarly in body Acute toxicity (human volunteers) Mild eye irritation Narcosis Subchronic toxicity Reversible irritation of respiratory tract Fatty liver Narcosis Dermally reversible irritation at the site of application Conclusion Relatively nontoxic chemical Narcosis, mild organ pathology and irritation of respiratory tract Effects appear only at vapor exposures > 250 ppm

Dose-response assessment Acute strong exposure 15 minutes of vapor concentrations of TCA increasing from 0 to 2650 ppm Mild eye irritation at ppm Throat irritation at pm Lightheadedness at 2600 ppm Inability to stand at 2650 ppm Chronic exposure Threshold assumed NOEL for lifetime continuous exposure for humans estimated as 50 ppm (factor 5) Equals to 21mg/kg*day (weight 70 kg, breathes 18 m3/day)

Exposure assessment Source Domestic wells TCA has been widely used as an industrial degreasing solvent Spills and leaking from undergound tanks have contaminated the soil From soil TCA readily leches to groundwater Routes of exposure Ingestion of contaminated water Dermal contact with contaminated water (bath, shower) Dermal contact with vapors volatilizing from the surface of contaminated water (bath, shower) Inhalation of vapors volatilizing from the surface of contaminated water (bath, shower, toilet) Total dose Worst case exposure: 1 bath per day + staying in bathroom for 1 hour + ingestion of 2 litres 0,0286 ug/kg*day + 0,0478 ug/kg*day = 0,0764 ug/kg*day (Water containing 1 ppb TCA)

Risk characterization TCA is a relatively nontoxic chemical No irreversible injury such as mutation, terata, or cancer Can cause narcosis, mild liver injury, and irritation of the respiratory tract (reversible) With safety factor of 10 used for each (1) variability in species, (2) variability in individual humans and (3) exposure to TCA from other sources, a nontoxic level of TCA in domestic water is estimated to be 270 ppb Highest level found (8800 ppb) still only 1/30 of NOEL The 2nd highest level (150 ppb) below the nontoxic level Estimate includes a large safety margin, but considering the uncertainties one should aim for lowest practical dose levels anyway

Thank you! Questions?