Effect of carbon black exposure on respiratory function and symptoms.

Carbon black is a widely used pigment and filler. Some, but not all, previous studies have suggested an effect of long-term exposure upon the lungs. Carbon black production facility employees (1755) participated in the third round of the industry-wide medical surveillance testing. They were employed in 22 North American plants. Spirometry and a systematically administered questionnaire were included in the year 2000 round of the industry-wide medical surveillance program. Industrial hygiene data from an industry-wide survey in 2000-2001, as well as all available exposure assessment data collected since 1979, were integrated with process questionnaires and exposure rating questionnaires completed by plant personnel. Analyses included multiple linear regression and categorical data analyses. Multiple regression analyses showed statistically significant, consistent relationships between cumulative exposure and small reductions in forced expiratory volume in 1 second (FEV 1 ) but not with other spirometry parameters. The estimated slopes were - 2 mL IEV 1 per mg-year/m 3 of cumulative 'total' dust exposure and - 0.7 mL FEV 1 per mg-year/m 3 of cumulative exposure for the inhalable fraction. In addition, heavy cumulative exposures were associated with a small increase in chronic bronchitis in nonsmokers. Recent exposures, typically much lower than in the past, were not demonstrated to be associated with these effects. Consistent with good occupational hygiene practice for any contaminant, workplace exposures to carbon black should be controlled to lowest practical levels.