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Step 1.5 Identifying Comparison Values

Advanced Exercise

Comparing maximum air concentration values to air comparison values

Acetone, methylene chloride, and 1,1,2-trichloroethane were detected in air samples taken at the Oak Estates site.

The health assessor then compared the maximum concentration of each of the three chemicals with air comparison values.

Acetone in air

The maximum concentration of acetone detected was 13,700 micrograms per cubic meter. The environmental media evaluation guides for acetone are 30,000 micrograms per cubic meter for chronic and intermediate exposure, and 60,000 micrograms per cubic meter for acute exposure.

There is no cancer risk evaluation guide for acetone because acetone has not been found to be associated with cancer in humans.

Because the maximum acetone level detected was lower than all of the comparison values, no further evaluation is needed.

Methylene chloride in air

The maximum concentration of methylene chloride detected in ambient air at Oak Estates was 112 micrograms per cubic meter. The environmental media evaluation guides for methylene chloride are 1,000 micrograms per cubic meter for chronic and intermediate exposure, and 2,000 micrograms per cubic meter for acute exposure. The cancer risk evaluation guide for methylene chloride is 3 micrograms per cubic meter.

Further evaluation of methylene chloride is necessary because the chemical was found at levels above the cancer risk evaluation guide.

1,1,2-Trichloroethane in air

The maximum concentration of 1,1,2-trichloroethane detected in air samples from the site was 31.2 micrograms per cubic meter.

No environmental media guides are available for 1,1,2-trichloroethane, but the cancer risk evaluation guide for the chemical is 0.06 micrograms per cubic meter.

Because the concentration of 1,1,2-trichloroethane detected is higher than the cancer risk evaluation guide, further evaluation is necessary.

Comparing maximum soil concentration values to soil comparison values

Aroclor 1254, arsenic, and methylene chloride were found in soil samples taken from the Oak Estates site.

The health assessor then compared the maximum concentration of each chemical with soil comparison values.

Aroclor 1254 in soil

The maximum concentration of Aroclor 1254 detected in soil samples from the site was 14 parts per million. No cancer risk evaluation guide exists for Aroclor 1254. The environmental media evaluation guide for an adult is 10 parts per million, while the environmental media evaluation guide for a child is 1 part per million.

Further evaluation of Aroclor 1254 is necessary because the maximum concentration is above the comparison values for both children and adults.

Arsenic in soil

Arsenic was detected in soil samples from the site at a maximum concentration of 11 parts per million. The adult environmental media evaluation guide for arsenic in soil is 200 parts per million; for a child, the environmental media evaluation guide is 20 parts per million. The cancer risk evaluation guide for arsenic in soil is 0.5 parts per million.

Further evaluation of arsenic is necessary because the maximum concentration of arsenic detected, 11 parts per million, is higher than the cancer risk evaluation guide of 0.5 parts per million.

Methylene chloride in soil

The maximum concentration of methylene chloride detected in soil from the site was 3.5 parts per million. The environmental media evaluation guide for methylene chloride in soil is 3,000 parts per million for a child and 40,000 parts per million for an adult. The cancer risk evaluation guide for methylene chloride in soil is 90 parts per million.

No further evaluation of methylene chloride in soil is necessary because the maximum concentration detected is below all of the comparison values.

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