Difference between revisions of "TCA in groundwater"
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| Line 4: | Line 4: | ||
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 | ||
| Line 22: | Line 23: | ||
** 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 | ||
| Line 40: | Line 38: | ||
== 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''' | ||
| Line 58: | Line 60: | ||
* 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''' | ||
| Line 64: | Line 66: | ||
* 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.
Contents
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
