TCA in groundwater: Difference between revisions
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Mikko Pohjola<br> | Mikko Pohjola<br> | ||
Juha Villman<br> | Juha Villman<br> | ||
Anne Karvonen | |||
'''James L. Byard: Hazard Assessment of 1,1,1-Trichloroethane in Groundwater''' | '''James L. Byard: Hazard Assessment of 1,1,1-Trichloroethane in Groundwater''' | ||
Focus: 1,1,1-Trichloroethane in Groundwater | |||
Scope: Looking at Santa Clara Valley (Silicon Valley) in California, considering primarily TCA hazard to humans. Other exposures, besides exposure to TCA in groundwater taken from wells, excluded. | |||
== Identification of Hazard == | == Identification of Hazard == | ||
* TCA is absorbed efficiently from the gastrointestinal tract and approximately with 30% efficiency from the lungs | |||
* TCA is absorbed from the gastrointestinal tract and 30 % from the lungs | |||
* Chemical is rapidly distributed to all tissues via bloodstream | * Chemical is rapidly distributed to all tissues via bloodstream | ||
* Chronic toxicity | * Chronic toxicity | ||
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** These results can be explained by butylene oxide present in some commercial formulations 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 | * No teratogenic effects in rodents exposed to TCA | ||
* High dose of TCA can cause: | * High dose of TCA can cause: | ||
** Narcosis | ** Narcosis | ||
** Mild organ pathology | ** Mild reversible organ pathology | ||
** | ** Reversible irritation of respiratory tract | ||
== Dose-Response assessment == | == Dose-Response assessment == | ||
* 15 minutes of vapor concentrations of TCA increasing from 0 to 2650 ppm | * 15 minutes of vapor concentrations of TCA increasing from 0 to 2650 ppm | ||
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== Exposure assessment == | == Exposure assessment == | ||
Source: | |||
* Domestic wells (incl. purveyors 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: | |||
*ingestion of contaminated water | |||
*dermal contact with contaminated water | |||
**dermal | *dermal contact with vapors volatilizing from the surface of contaminated water | ||
* | *inhalation of vapors volatilizing from the surface of contaminated water | ||
'''Ingestion''' | '''Ingestion''' | ||
* 2 litres of water per day per 70 kg | * 2 litres of water per day per 70 kg | ||
* Complete absorption | * Complete absorption | ||
* '''0,0286 ug/kg day''' (Water containing 1 ppb TCA) | * '''0,0286 ug/kg*day''' (Water containing 1 ppb TCA) | ||
'''Toilet bowl''' | '''Toilet bowl''' | ||
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* 70 kg body weight | * 70 kg body weight | ||
* 30 % uptake from the lungs | * 30 % uptake from the lungs | ||
* '''0,00032 ug/kg day''' (Water containing 1 ppb TCA) | * '''0,00032 ug/kg*day''' (Water containing 1 ppb TCA) | ||
'''Shower''' | '''Shower''' | ||
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* 10 minute shower | * 10 minute shower | ||
* 50 litres of water containing 1 ppb TCA | * 50 litres of water containing 1 ppb TCA | ||
* '''0,00358 ug/kg day''' | * '''0,00358 ug/kg*day''' | ||
* Additional dermal vapor absortion is 1 % of the inhalation dose | * Additional dermal vapor absortion is 1 % of the inhalation dose | ||
* '''0,0072 ug/kg day''' | * '''0,0072 ug/kg*day''' | ||
'''Bath''' | '''Bath''' | ||
* 100 litres of water at 50 celcius for 20 minutes | * 100 litres of water at 50 celcius for 20 minutes | ||
* Total inhalation is '''0,00179 ug/kg day'''(Water containing 1 ppb TCA) | * Total inhalation is '''0,00179 ug/kg*day'''(Water containing 1 ppb TCA) | ||
* Dermal absorption from the vapor is 1 % | * Dermal absorption from the vapor is 1 % | ||
* Dermal absorption from the bath water is '''0,0457 ug/kg day''' | * 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 from bath (inhale, water and vapor) is '''0,0475 ug/kg*day''' | ||
'''Total dose''' | '''Total dose''' | ||
*Worst case bathroom exposure: 1 bath per day + staying bathroom for 1 hour + ingestion of 2 litres | *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) | * 0,0286 ug/kg*day + 0,0478 ug/kg*day = '''0,0764 ug/kg*day''' (Water containing 1 ppb TCA) | ||
== Risk Characterization == | == Risk Characterization == | ||
* TCA is a relatively nontoxic chemical | |||
* TCA does not appear to produce irreversible injury such as mutation, terata, or cancer | |||
* Based on a lifetime continuous exposure, NOEL is 21 mg/kg*day | |||
* With safety factor 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 | |||
* The (by far) highest level of TCA found on the area | |||
Revision as of 05:42, 14 September 2006
Introduction to Environmental risk analysis - course
Groupwork
Mikko Pohjola
Juha Villman
Anne Karvonen
James L. Byard: Hazard Assessment of 1,1,1-Trichloroethane in Groundwater
Focus: 1,1,1-Trichloroethane in Groundwater Scope: Looking at Santa Clara Valley (Silicon Valley) in California, considering primarily TCA hazard to humans. Other exposures, besides exposure to TCA in groundwater taken from wells, excluded.
Identification of Hazard
- TCA is absorbed efficiently from the gastrointestinal tract and approximately with 30% efficiency 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
- High dose of TCA can cause:
- Narcosis
- Mild reversible organ pathology
- Reversible irritation of respiratory tract
Dose-Response assessment
- 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
Source:
- Domestic wells (incl. purveyors 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:
- ingestion of contaminated water
- dermal contact with contaminated water
- dermal contact with vapors volatilizing from the surface of contaminated water
- inhalation of vapors volatilizing from the surface of contaminated water
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
- TCA is a relatively nontoxic chemical
- TCA does not appear to produce irreversible injury such as mutation, terata, or cancer
- Based on a lifetime continuous exposure, NOEL is 21 mg/kg*day
- With safety factor 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
- The (by far) highest level of TCA found on the area