Table 2.
Summary of variables used to model concentrations of HDI, uretidone, biuret, and isocyanurate in the breathing-zone of automotive spray painters
Type | Name | Description | Range of values | Mean value | Median value |
Classification | Booth typea | Type of ventilated paint booth | Downdraft, semi-downdraft, crossdraft | NA | NA |
Continuous | Airflow | Airflow inside the paint booth (m3 min−1) | 0–469 | 221 | 238 |
Booth volume | Volume of the paint booth (m3) | 55.3–684 | 101 | 95.2 | |
Experience | Experience spray painting cars (years) | 0.25–40 | 13.4 | 12 | |
Humidity | Average relative humidity (%) | 39.0–96.0 | 72.6 | 74.0 | |
Paint concentration (HDI)b | Concentration of HDI in paint (mg l−1) | 0.014–1060 | 280 | 259 | |
Paint concentration (uretidone)b | Concentration of uretidone in paint (mg l−1) | 0.060–20 900 | 880 | 68.2 | |
Paint concentration (biuret)b | Concentration of biuret in paint (mg l−1) | 1.00–23 800 | 2030 | 814 | |
Paint concentration (isocyanurate)b | Concentration of isocyanurate in paint (mg l−1) | 0.56–357 000 | 96 000 | 94 800 | |
Paint time | Time spent inside the booth painting (min) | 1.0–56.0 | 8.49 | 6.50 | |
Temperature | Estimate temperature during spraying (°C) | 23.9–33.9 | 25.0 | 23.9 | |
Total time | Total operating time of the sampling pumps (min) | 3.0–105 | 21.4 | 17.0 | |
Dichotomous | Enclosure | Type of enclosure surrounding the paint booth | 1: curtain, 0: wall | 0.063 | 0 |
Gun type | Type of spray gun used for applying paint | 1: HVLP, 0: conventional | 0.92 | 1 | |
Paint type | Type of paint applied to the surface of the vehicle | 1: clear coat, 0: other | 0.92 | 1 | |
Sampler type | Type of sampler used to monitor air concentration | 1: two stage, 0: one stage | 0.66 | 1 |
Because booth type is a character variable use for classification, mean and median values could not be calculated (NA = non-applicable).
HDI, uretidone, biuret, and isocyanurate were non-detectable in 3.1, 36, 17, and 1.0% of all paint samples, respectively. Multiple imputation (n = 10 imputed datasets) was used to impute paint-sampling data below detection limits.