Difference between revisions of "TCA in groundwater"
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Revision as of 12:49, 13 September 2006
Introduction to Environmental risk analysis - course
Groupwork
Mikko Pohjola
Juha Villman
James L. Byard: Hazard Assessment of 1,1,1-Trichloroethane in Groundwater
Contents
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
