Table 1.
Summary of the chlorinated solvents measurement database compiled from the published literature and NIOSH reports
| Characteristic | Methylene chloride | 1,1,1-trichloroethane | Trichloroethylene |
| Total reported levels | 1641 | 1441 | 641 |
| Excluded in data cleaning efforta | −89 | −88 | −84 |
| Excluded for missing valuesb | −198 | −263 | −52 |
| Excluded for ‘high judgment’c | −82 | −143 | −21 |
| Retained for modeling | 1272 (78%) | 947 (66%) | 484 (76%) |
| Sourced | |||
| Percent published literature | 15 | 2 | 30 |
| Percent NIOSH HHE report | 63 | 89 | 65 |
| Percent NIOSH IWS report | 22 | 9 | 6 |
| Sample sized | |||
| Range (mean) | 1–110 (3.4) | 1–141 (1.3) | 1–212 (3.2) |
| Percent individual measurements | 92 | 99 | 91 |
| Percent sample size estimated | 5.0 | 0 | 0.8 |
| Reported levelsd | |||
| Percent censored at the LOD | 12 | 23 | 12 |
| Percent estimated | 2.3 | 0.7 | 1.4 |
| Measurement duration and typed | |||
| Percent long-term personal | 61 | 56 | 37 |
| Percent short-term personal | 11 | 8 | 10 |
| Percent long-term area | 25 | 31 | 25 |
| Percent short-term area | 4 | 5 | 27 |
| Measurement yeard | |||
| Range (median) | 1956–2001 (1983) | 1970–1996 (1983) | 1940–1998 (1982) |
| Percent prior to 1970 | 1 | 0 | 19 |
| Percent in 1970–1979 | 22 | 8 | 7 |
| Percent in 1980–1989 | 60 | 72 | 64 |
| Percent in 1990 or later | 16 | 20 | 10 |
a
The data cleaning effort included identifying and excluding duplicate measurements and measurements collected under unusual conditions (e.g. accident investigations).
b
Measurements with missing values for one or more exposure determinant or measurement characteristic were excluded from the modeling process.
c
Measurements with approximately half or more of the exposure determinants based on ‘judgment’ were excluded from the modeling process.
d
For reported levels that were retained for modeling.