TCA in groundwater

Introduction to Environmental risk analysis - course

Groupwork

Mikko Pohjola
Juha Villman

James L. Byard: Hazard Assessment of 1,1,1-Trichloroethane in Groundwater

Identification of Hazard

In text: chapters 8 Toxicology & 9 Estimation of nontoxic dose

• TCA has been used as an industrial degreasing solvent
• TCA is absorbed from the gastrointestinal tract and 30 % from the lungs
• Chemical is rapidly distributed to all tissues via bloodstream
• Chronic toxicity
  • Reported in several studies for no toxicity, no excess cancers, no marked oncogenic effect, no effect on mortality or body weight
  • One study reported excess of leukemias in rats exposed to TCA
• Only few weakly positive results for mutagenicity of TCA
  • These results can be explained by butylene oxide present in some commercial formulations of TCA
• No teratogenic effects in rodents exposed to TCA
• TCA is relatively nontoxic chemical
• High dose of TCA can cause:
  • Narcosis
  • Mild organ pathology
  • Irritation of respiratory tract

Dose-Response assessment

In text: 8 Toxicology & 9 Estimation of nontoxic dose

• 15 minutes of vapor concentrations of TCA increasing from 0 to 2650 ppm
  • Mild eye irritation at 1000 - 1100 ppm
  • Throat irritation at 1900 - 2000 pm
  • Lightheadedness at 2600 ppm
  • Inability to stand at 2650 ppm

Exposure assessment

In text: 6 Exposure & 7 Determination of dose

• Domestic wells
• Routes
  • ingestion
  • dermal
  • lungs

Ingestion

• 2 litres of water per day per 70 kg
• Complete absorption
• 0,0286 ug/kg day (Water containing 1 ppb TCA)

Toilet bowl

• 1 h/day
• respiration rate of 18m³/day
• 70 kg body weight
• 30 % uptake from the lungs
• 0,00032 ug/kg day (Water containing 1 ppb TCA)

Shower

• Highest inhalation exposure due to large volume of hot water and small air volume of a shower stall
• 10 minute shower
• 50 litres of water containing 1 ppb TCA
• 0,00358 ug/kg day
• Additional dermal vapor absortion is 1 % of the inhalation dose
• 0,0072 ug/kg day

Bath

• 100 litres of water at 50 celcius for 20 minutes
• Total inhalation is 0,00179 ug/kg day(Water containing 1 ppb TCA)
• Dermal absorption from the vapor is 1 %
• Dermal absorption from the bath water is 0,0457 ug/kg day
• Total dose from bath (inhale, water and vapor) is 0,0475 ug/kg day

Total dose

• Worst case bathroom exposure: 1 bath per day + staying 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

In text: 10 Conclusions & 9 Estimation of nontoxic dose