title: Updated epidemiological study of workers at two California petroleum refineries, 1950-95.
abstract: OBJECTIVE
  To further assess the potential role of occupational exposures on mortality, a second update of a cohort study of workers at two petroleum refineries in California was undertaken.
  
  
  METHODS
  Mortality analyses were based on standardised mortality ratios (SMRs) and 95% confidence intervals (95% CIs) using the general population of California as a reference. Additional analyses of lymphatic and haematopoietic cancer deaths and diseases related to asbestos were undertaken.
  
  
  RESULTS
  The update consisted of 18,512 employees, who contributed 456,425 person-years of observation between 1950 and 1995. Both overall mortality and total cancer mortality were significantly lower than expected, as were several site specific cancers and non-malignant diseases. In particular, no significant increases were reported for leukaemia cell types or non-Hodgkin's lymphoma. Mortality excess from multiple myeloma was marginally significant. The excess was confined to employees enrolled before 1949. Furthermore, there was no significant upward trend based on duration of employment, which argues against a causal interpretation relative to employment or exposures at the refineries. No increase was found for diseases related to asbestos: pulmonary fibrosis; lung cancer; or malignant mesothelioma. There was no significant increase in mortality from any other cancers or non-malignant diseases.
  
  
  CONCLUSIONS
  This second update provides additional reassurance that employment at these two refineries is not associated with increased risk of mortality.
authors.affiliation: Toxicology and Health Risk Assessment, Chevron Texaco Energy Research and Technology Company, Richmond, CA 94802-0627, USA.
authors.forename: K P
authors.initials: KP
authors.lastname: Satin
authors.forename: W J
authors.initials: WJ
authors.lastname: Bailey
authors.forename: K L
authors.initials: KL
authors.lastname: Newton
authors.forename: A Y
authors.initials: AY
authors.lastname: Ross
authors.forename: O
authors.initials: O
authors.lastname: Wong
mesh_terms: D001194:Asbestos / Q000009:adverse effects; D002140:California / Q000453:epidemiology; D002423:Cause of Death; D015331:Cohort Studies; D019652:Extraction and Processing Industry / Q000706:statistics & numerical data*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D009369:Neoplasms / Q000401:mortality*; D009784:Occupational Diseases / Q000401:mortality*; D016273:Occupational Exposure / Q000706:statistics & numerical data*; D010578:Petroleum / Q000009:adverse effects; D012307:Risk Factors
chemical_list: D010578:Petroleum; D001194:Asbestos