An updated cause specific mortality study of petroleum refinery workers

Area of Science:

• Occupational Health
• Epidemiology
• Environmental Health

Background:

• A cohort study of 14,074 Chevron USA refinery employees in California was updated to examine mortality patterns.
• The previous study indicated lower mortality rates among these workers compared to the general population.

Purpose of the Study:

• To update the mortality analysis with six additional years of follow-up data (1981-1986).
• To further investigate specific causes of death and potential occupational associations within the refinery worker cohort.

Main Methods:

• A cohort study design was employed, analyzing mortality data from 14,074 employees.
• Standardized mortality ratios (SMR) were calculated by comparing observed deaths to expected deaths based on US and California general population rates.
• Follow-up data included 941 deaths over the extended period.

Main Results:

• Overall mortality (SMR = 73) and cancer mortality (SMR = 81) remained significantly lower than the general US population.
• Elevated mortality was observed for suicide compared to the US, but not when compared to California rates.
• Leukemia and lymphoreticulosarcoma showed patterns suggestive of occupational links, especially for employees hired before 1949 and Richmond workers for lymphoreticulosarcoma.

Conclusions:

• The updated study reaffirms lower overall and cancer mortality in Chevron refinery workers.
• Specific occupational risks for leukemia and lymphoreticulosarcoma may exist, particularly for long-term employees hired before 1949.
• Further investigation into specific exposures and occupational links is warranted for certain cancers.