Trends in cigarette smoking among refinery and petrochemical plant employees with a discussion of the potential impact on lung cancer

To examine trends in cigarette smoking prevalence and intensity among petroleum industry employees over a 22-year period, from 1976 to 1997, and to evaluate the hypothesis that the (about 20%) lower lung cancer mortality, when compared with the general population, among these workers is due to lower average cigarette consumption. Self-reported smoking prevalence and intensity (number of cigarettes smoked per day) data were available from the Shell Health Surveillance System for approximately 5,400 employees in the 1970s, 11,000 in the 1980s, and 8,300 in the 1990s. Data were analyzed by gender, time period, and work status (production vs. staff). During the 22-year study period, smoking prevalence dropped significantly in this working population. When compared with the general US population, smoking prevalence trends were very similar. For the entire employee population, smoking prevalence was highest for women working in production (hourly) jobs. While smoking prevalence was higher among production employees than among staff employees, daily cigarette consumption was slightly lower. Cigarette consumption among Shell employees was similar to that in the US in the 1970s, but lower in the 1980s and 1990s. By applying smoking consumption data from the 1970s, the ratio of weighted lung cancer relative risks for Shell employees and the US general population was 0.98. In other words, the lung cancer mortality rate of refinery and petrochemical employees would be adjusted upward by 2% if one were to remove the influence of smoking consumption by Shell employees. Based on our data, it is unlikely that differences in smoking prevalence and intensity between refinery/petrochemical workers and the general population could account for the lower risk of lung cancer mortality reported in the literature.