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PubMed2007

Inter-rater agreement in the assessment of exposure to carcinogens in the offshore petroleum industry.

OBJECTIVES: To evaluate the reliability of an expert team assessing exposure to carcinogens in the offshore petroleum industry and to study how the information provided influenced the agreement among raters. METHODS: Eight experts individually assessed the likelihood of exposure for combinations of 17 carcinogens, 27 job categories and four time periods (1970-1979, 1980-1989, 1990-1999 and 2000-2005). Each rater assessed 1836 combinations based on summary documents on carcinogenic agents, which included descriptions of sources of exposure and products, descriptions of work processes carried out within the different job categories, and monitoring data. Inter-rater agreement was calculated using Cohen's kappa index and single and average score intraclass correlation coefficients (ICC) (ICC(2,1) and ICC(2,8), respectively). Differences in inter-rater agreement for time periods, raters, International Agency for Research on Cancer groups and the amount of information provided were consequently studied. RESULTS: Overall, 18% of the combinations were denoted as possible exposure, and 14% scored probable exposure. Stratified by the 17 carcinogenic agents, the probable exposure prevalence ranged from 3.8% for refractory ceramic fibres to 30% for crude oil. Overall mean kappa was 0.42 (ICC(2,1) = 0.62 and ICC(2,8) = 0.93). Providing limited quantitative measurement data was associated with less agreement than for equally well described carcinogens without sampling data. CONCLUSION: The overall kappa and single-score ICC indicate that the raters agree on exposure estimates well above the chance level. The levels of inter-rater agreement were higher than in other comparable studies. The average score ICC indicates reliable mean estimates and implies that sufficient raters were involved. The raters seemed to have enough documentation on which to base their estimates, but provision of limited monitoring data leads to more incongruence among raters. Having real exposure data, with the inherent variability of such data, apparently makes estimating exposure in a rigid semiquantitative manner more difficult.

Carcinogens↗
PubMed1999

Industrial dental erosion: a cross-sectional, comparative study.

Occupational exposure to sulphuric acid mist (H2SO4) is a health hazard. The threshold limit value-time weighted average (TLV-TWA) of exposure to H2SO4 recommended by the American Conference of Governmental Industrial Hygienists (ACGIH, 1994-1996) is 1 mg/m3. This single-blind study conducted in an electro-winning facility in South Africa, compared dental erosion of anterior and premolar teeth of male workers exposed daily to H2SO4 in an exposed group (H2SO4 range: 0.3 mg/m3-1 mg/m3) and an unexposed group (H2SO4 range: 0.1 mg/m3-0.3 mg/m3). The exposed group comprised all workers at the facility exposed to the aforesaid range of H2SO4 (N = 103). A total of 102 unexposed subjects similar in composition with respect to age and length of service were randomly selected from the rest of the 700 workers at the facility. A questionnaire was administered to seek information on possible worker habits associated with dental erosion and to determine perceptions of oral function. Clinical examinations assessed prevalence and severity of dental erosion. The mean age of subjects was 31.4 years and mean length of service 4.2 years. In the exposed group 48% complained of pain and sensitivity on their teeth compared with the 31% of unexposed persons (P = 0.020). Dental erosion was present in exposed (96%) and unexposed (75%) subjects. Exposed subjects were more likely to develop erosion than unexposed subjects, the odds ratio being 5.531 within the confidence limits 2.167 < OR < 14.117. There was a significant difference in the severity of tooth surface loss between exposed and unexposed groups (P = 0.001). Dental erosion was most severe in the anterior teeth and occurred mostly on the labial and incisal surfaces.

Adult↗
PubMed2003

Effect of lead exposure on the immune response of some occupationally exposed individuals.

Lead is a ubiquitous pollutant in the industrial environment, which poses serious threats to human health. In the past 20 years increasing attention has been paid to the effects of lead exposure on health. This toxic metal alters the immune response of animals as well as humans. To study the immunological effects of occupational exposure to lead, we examined lymphocyte proliferation, natural killer (NK) cell cytotoxicity and interferon-gamma production with peripheral blood mononuclear cells (PBMCs) of individuals occupationally exposed to lead. We selected three different groups of individuals exposed to lead: three-wheeler drivers (30), battery workers (34) and silver jewelery makers (20); and unexposed healthy volunteers (30) as control for comparison. Our results indicate that though lymphocyte proliferation to phytohaemagglutinin (PHA) is inhibited in lead exposed individuals as compared with unexposed volunteers, there is no correlation between inhibition of lymphocyte proliferation and blood lead level. NK cell cytotoxicity remains unaffected in individuals exposed to lead as compared with controls. On the other hand, we observed that interferon-gamma (IFN-gamma) was significantly elevated in T cell mitogen, PHA, stimulated PBMCs culture supernatant of lead exposed individuals. We found significant positive correlation between blood lead levels and IFN-gamma produced in culture supernatant on stimulation with PHA. In brief, this study demonstrates that lead can affect the immune response of the occupationally exposed individuals such as three-wheeler drivers, battery reconditioning workers and silver jewelery makers.

Cytotoxicity Tests, Immunologic↗
PubMedDate not supplied

[The accumulation of the technogenic radionuclides by mushrooms in the area affected by the activity of the Krasnoyarsk mining-and-chemical industrial complex].

The radionuclide content was measured in mushrooms collected in different sites situated in the zone of the radiation influence on the Mining-and-Chemical Combine at Zheleznogorsk and on the control site, near Krasnoyarsk, in 2002-2004. The analytical investigations of fruiting bodies of 12 mushroom species have revealed three gamma-emitting radionuclides: 7Be, 40K (natural) and 137Cs (artificial). It was found that only three species contain 7Be; activity concentration of 40K is not species- and site-dependent, averaging 1600 Bq/kg. All collected samples contain 137Cs, and its accumulation by mushrooms is species-specific. Suillus concentrates more 137Cs activity than other species and can be used as a bioindicator of soil contamination with radiocesium. The average activity concentration of 137Cs in Suillus granulatus collected in the sites subjected only to aerosol discharges of the MCC is more than twice higher than 137Cs content of the mushrooms collected in the control site--"Krasnoyarsk". The maximum activity concentration of 137Cs in Suillus samples collected in the sites that receive 137Cs with the flood water is an order of magnitude higher, amounting to 8624 Bq/kg. The analysis of the radionuclide distribution in a mushroom shows that 40K activity concentration is the same in caps and stems of Suillus, and 137Cs concentration in Suillus caps is 1.7-2.3 times higher than in stems. Binding of radionuclides by mushroom biomass was determined by chemical fractionation; it was found that the highest activities of 137Cs and 40K are in the exchange-adsorption fraction (56 to 71% of the total content of a radionuclide) and in the organic fraction (23 to 37%). Calculations were made for determination of the coefficients of 40K and 137Cs transfer from the soil to the fruiting body of Suillus.

Agaricales↗
PubMed2000

Update of a study of crude oil production workers 1946-94.

OBJECTIVE: To update information on workers in the petroleum industry engaged in the production of crude oil to determine whether the patterns of mortality have changed with 14 additional years of follow up. METHODS: All workers were employed at company production and pipeline locations sometime during 1946-94. The cohort now consists of 24 124 employees with an average of 22 years of follow up. RESULTS: The overall mortality, and most cause specific mortalities were lower than or similar to those for the general United States population. For white men (81% of the cohort), there were 4361 observed deaths and 5945 expected, resulting in a significantly lower standardised mortality ratio (SMR) of 73. There were significant deficits for all the leading causes of death in the United States including all cancers, cancer of the lung, stroke, heart disease, respiratory disease, and accidents. Slightly increased mortality was found for cancer of the prostate, cancer of the brain and central nervous system, and cancer of other lymphatic tissue. For benign and unspecified neoplasms, the SMR was 152 (95% confidence interval (95% CI) 95 to 230). There was a significant increase for acute myelogenous leukaemia that was restricted to people who were first employed before 1940 and who were employed in production and pipeline jobs for >30 years. Overall mortality patterns for non-white men and women were similar to those for white men. Mortality patterns for white men were also examined by duration of employment, time first employed, and by job group. CONCLUSIONS: The results of the updated study showed a favourable mortality experience for crude oil production workers compared with the United States population.

Cause of Death↗
PubMed2001

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

OBJECTIVE: 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. METHODS: 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). RESULTS: 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. CONCLUSIONS: 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.

Adult↗
PubMed2003

Demographic and lifestyle predictors of body mass index among offshore oil industry workers: cross-sectional and longitudinal findings.

BACKGROUND: Significant overweight among offshore workers on North Sea oil and gas installations has been linked to high calorie intake, lack of active leisure-time pursuits, and environmental factors conducive to weight gain. However, the prevalence of overweight among offshore workers has not been examined in recent data, and no longitudinal studies of body mass index (BMI) in this occupational group have been reported. Aims The present study sought to examine BMI levels in a sample of UK offshore personnel, and to evaluate demographic factors, smoking and work-related physical activity as predictors of BMI, and 5 year change in BMI. METHODS: Survey data (including age, education, marital status, work-related physical activity and height/weight) were collected in 1995 from male workers on 17 North Sea installations (n = 1581, 83% response rate); follow-up data were obtained in 2000 (n = 354, 34.9% of the potential sample). RESULTS: Overall mean BMI was 25.6 (2.8) kg/m(2): rates of obesity (BMI > 30) and overweight (BMI = 25-30) were 7.5 and 47.3%, respectively. Mean age was 38.7 (8.9) years; linear and quadratic age terms predicted BMI. Age-adjusted BMI values were very similar to those reported from other offshore studies over the past 15 years. Age, marital status, education, smoking and physical activity significantly predicted baseline BMI, but only age (and some interactive effects) predicted 5 year BMI change. CONCLUSIONS: The present age-adjusted BMI values were closely similar to those found offshore in the mid-1980s, but also to recent national data; thus, North Sea personnel do not appear to reflect current population trends towards increased BMI levels. This result accords with the emphasis now given to health promotion (particularly dietary change) on offshore installations; the present findings also highlight the need to focus these initiatives on workers with sedentary jobs and/or low education.

Adult↗
PubMed2003

Air sampling methodology for asphalt fume in asphalt production and asphalt roofing manufacturing facilities: total particulate sampler versus inhalable particulate sampler.

In 2000, the American Conference of Governmental Industrial Hygienists (ACGIH(R)) changed its 1971 threshold limit value (TLV) for 8-hour time-weighted average (TWA) exposure to asphalt from 5 mg/m(3) total particulate (generally < or =40 micrometer [microm] diameter) to 0.5 mg/m(3) inhalable particulate (< or =100 microm aerodynamic diameter) as benzene-soluble aerosol. To date, no inhalable particulate sampling method has been standardized and validated for asphalt fume. Furthermore, much of the historical data were collected using total particulate samplers, and the comparability of total versus inhalable size fractions of asphalt fume is not known. Therefore, the present study compared results from two types of asphalt fume samplers: 1) a traditional total particulate sampler with a 37-mm filter in a closed-face cassette with a 4-mm orifice (NIOSH 5042) versus (2) an inhalable particulate sampler designed by the IOM with a 15-mm orifice. A total of 75 simultaneous pairs of samples were collected, including personal and area samples from 19 roofing and asphalt production facilities operated by 7 different manufacturers. Each sample was analyzed for total mass collected and for benzene-soluble mass. Data from the two sampling methods (total versus inhalable) were comparable for asphalt fumes up to an aerosol concentration of 10 mg/m(3). However, we conclude that the traditional total particulate method is preferable, for this reason: The vast majority of asphalt fume particles are <12.5 microm in diameter. The traditional sampler is designed to collect primarily particles < or =40 microm, while the IOM sampler is optimized for collecting particles < or =100 microm. Thus, the traditional sampler is less likely than the IOM sampler to collect the larger-size fraction of airborne particles, most of which are non-asphalt dust.

Aerosols↗
PubMed1998

A comparative assessment of liver function in workers in the petroleum industry.

OBJECTIVES: The group studied included 666 workers from the benzene (n = 30), xylenes (n = 144), ethylene oxide (n = 91), 1,3-butadiene (n = 110) and transport and mechanisation (n = 82) departments of a petrochemical plant in Bulgaria. The leading hazards for the particular departments are as follows: Benzene: benzene (up to ten times the threshold limit value; TLV): xylenes: benzene (up to nine times TLV) and xylenes (up to 1.6 times TLV); ethylene oxide: ethylene oxide (up to 20 times TLV) and ethylene (up to 30 times TLV); divinyl: 1,3-butadiene (five times TLV) and acetonitrile (six times TLV); transport and mechanisation: benzene, xylenes and pentane (0.7-10 times TLV). METHODS: The functional status of the liver was assessed by clinical (medical check-up), echographic and biochemical (ASAT, ALAT, APh, gamma-GT, lipid fractions, reduced glutathione and SH groups) investigations. Biochemical analyses were performed with POINTE 190 (USA). The results obtained were compared with those of a control group (n = 150), consisting of subjects with no occupational exposure to chemical hazards. RESULTS: Comparisons showed that the metabolic disturbances determined were most significant in workers from the ethylene oxide department. Significant decreases in the serum levels of reduced glutathione (up to 48%) and of thiol groups (with 23%), increased enyzme activity (up to 18%) and lipid fractions (up to 24%) were observed. In the benzene and xylenes departments, deviations in the indices studied were equally manifest. In workers exposed to 1,3-butadiene, the changes in lipid indices were prevalent (registered in 25% of the studied persons). The staff in transport and mechanisation showed deviations in enzyme indices at a slight increase of the lipid fractions. The changes determined in serum biochemical characteristics corresponded to the clinical findings--hepatomegaly, confirmed echographically in 10%-20% in the different departments. CONCLUSIONS: The results obtained followed the exposure-response relationship. The deviations registered in workers with a length of service of more than 10 years were the most significant. The occupational genesis of the determined disturbances was confirmed in 11 subjects.

Adult↗
PubMed2001

[Liver function of workers occupationally exposed to mixed organic solvents in a petrochemical industry].

A descriptive and cross sectional study was conducted to determine whether hepatic function changes in workers occupationally exposed to a mixture of organic solvents, were due to the exposure or confusing factors. A non random sample of 77 workers, operators and supervisors of the Olefin Plant I and II of a petrochemical industry in Maracaibo, Venezuela, was used. Their mean age was 29 +/- 7 years, and had at least one year of exposure to the solvents. This sample was compared with a group of employees of the administrative offices or control panel workers, with a mean age of 36 +/- 8 year and with similar anthropometric characteristics. Workers with a known history of liver disease, blood transfusions and diabetes mellitus were excluded of the study. In addition to a complete occupational disease medical history and a physical examination, serum samples were obtained to determine the activity of the aspartato aminotransferase (AST), alanin aminotransferase (ALT), gamma glutamiltransferase (GGT), alkaline phosphatase (AF), the concentration of the total bile acids (BAS), the surface antigen of hepatitis B(HbsAg) and the hepatitis A virus antibodies: AntiHAV-IgG and the AntiHAV-IgM. An urine sample was taken and analyzed by standard methodology to determine urinary phenols. The air concentrations of benzene, ethylbenzene, toluene and xylene were analyzed by gas chromathography. The serum activities of the liver enzymes, the concentration of bile acids and urinary phenols were not influenced by the exposure to the solvents. The increase of the activity of GGT was associated with obesity and alcohol consumption. The antibodies of the surface antigen of hepatitis A-IgM were normal in both groups and the antibodies for the antigen of hepatitis A-IgG presented a prevalence of 6% in the exposed group and 9% in the non exposed not being associated with liver abnormalities. The individual air concentrations of the solvents were below the environmentally permissible concentrations, except one sample of benzene (1, 14 ppm) that was over the allowed limit. The total maximum concentration of the mixture of organic solvents, resulting of the sum of fractions of each organic solvent, was within the allowed limits. In conclusion, obesity and alcohol consumption, and not the occupational factors, seem to be responsible for the alteration in GGT in workers of these Olefin Plants.

Adult↗
PubMed1998

Workplace risk factors for cancer in the German rubber industry: Part 2. Mortality from non-respiratory cancers.

OBJECTIVES: To determine the mortality from non-respiratory cancers by work area among active and retired male workers of the German rubber industry. METHODS: A cohort of 11,633 male German workers was followed up for mortality from 1 January 1981 to 31 December 1991. Cohort members were active (n = 7536) or retired (n = 4127) on 1 January 1981 and had been employed for at least one year in one of five study plants producing tyres or technical rubber goods. Work histories were reconstructed from routinely documented "cost centre codes" and classified into six categories: I preparation of materials; II production of technical rubber goods; III production of tyres; IV storage and dispatch; V general service; VI others. Standardised mortality ratios (SMRs) and 95% confidence intervals (95% CIs), controlling for age and calendar year and stratified by work area (employment in respective work area for at least one year) and time related variables (year of hire, lagged years of employment in work area) were calculated from national mortality rates as the reference. RESULTS: Significant increases in mortality were found for pharyngeal cancer in work area IV (three deaths, SMR 486, 95% CI 101 to 1419), oesophageal cancer in work area III (11 deaths, SMR 227, 95% CI 114 to 407), and leukaemia in work areas I (11 deaths, SMR 216; 95% CI 108 to 387) and II (14 deaths, SMR 187; 95% CI 102 to 213). Furthermore, increased SMRs were found for stomach cancer in work area I (22 deaths, SMR 134; 95% CI 84 to 203), colon cancer in work area II (27 deaths, SMR 131, 95% CI 86 to 191), prostatic cancer in work area V (27 deaths, SMR 152, 95% CI 99 to 221), and bladder cancer in work areas IV (six deaths, SMR 253; 95% CI 93 to 551) and V (12 deaths, SMR 159, 95% CI 82 to 279). Mortality from cancer of the liver or gall bladder, pancreas and kidney, and from lymphomas was not substantially increased in any of the work areas. CONCLUSIONS: Mortality from cancer of several sites was associated with specific work areas. Some of these associations have been reported previously. Future analyses of our study will have to determine the role of specific exposures in the aetiology of these cancers.

Adult↗
PubMed2005

Mortality from lung and kidney disease in a cohort of North American industrial sand workers: an update.

BACKGROUND: A previously published cohort study of some 2670 employees of the North American sand industry, followed through 1994, provided strong evidence of a causal relationship between quartz exposure and death from both silicosis and lung cancer, after allowance for cigarette smoking and in the absence of known occupational carcinogens. Unexpectedly, a significant excess mortality from chronic non-malignant renal disease [observed 16; expected 7.6; standardized mortality ratio (SMR) 212] was also found, whereas deaths from renal cancer at this stage were close to expectation (observed 6; expected 5.2). OBJECTIVES: Our primary aim was to discover whether death from chronic renal disease was related to the estimated intensity of crystalline silica exposure. A further aim was to determine whether or not our previous estimates of lung cancer and silicosis risk were confirmed by mortality in the cohort 6 years later. METHODS: With help from the US National Death Index, surviving members of the cohort, with the exception of employees of a small plant in Canada, were traced through 2000. The cause of death was determined for all who had died, for comparison against National and State mortality rates. Nested case-referent analyses were then undertaken, as previously, of deaths from lung cancer and silicosis, plus end-stage renal disease and kidney cancer, in relation to quantitative re-estimates of quartz exposure. RESULTS: The total number of deaths through 1994 was 990; there were 231 additional deaths during the period 1995-2000. The SMRs were significantly higher in the later than the earlier period, mainly due to a relative increase in heart disease and external causes. The updated odds ratios for lung cancer and silicosis were almost identical to those published previously, with lung cancer risk again related to average silica concentration and cumulative exposure, but not to length of employment. In contrast, risks of neither end-stage renal disease nor renal cancer were related to cumulative exposure, although now based on 19 cases (SMR 239), and 10 cases (SMR 202), respectively, in fact, opposite trends were apparent for both diseases. However, because of the small numbers there was only limited power to assess the statistical significance of these trends or of any separate relationship with the duration or intensity of exposure. CONCLUSIONS: Our findings support a causal relationship between lung cancer and quartz exposure after allowance for cigarette smoking, in the absence of other known carcinogens, but failed to find similar evidence to explain the excess mortality from either chronic renal disease or kidney cancer.

Case-Control Studies↗
PubMed1998

South African asbestos: production, exports, and destinations, 1959-1993.

Production and export figures of South African asbestos were analyzed over 1959-1993. They show stable sales of chrysotile. Those of crocidolite and amosite reached their peaks in the mid-1970s, after which trade fell drastically, crocidolite to 5% of its earlier peak and amosite to nil. Factors responsible for these virtual collapses were health issues, stricter legislation in First World countries, and litigation. In 1992, 21 countries continued to import crocidolite, although in reduced quantities. In the early 1960s, Europe and North America were the major recipients of South African asbestos. By 1989-91, these regions were surpassed by the Far East, which took over 90% of chrysotile and 70% of amosite. For crocidolite at that time, the Middle East took nearly 40%, Europe 28%, and Africa 21%. This implies that the newly importing countries can confidently expect an increase in asbestos-related disease and death well into the twenty-first century, even if the trade ceased now.

Asbestos↗
PubMed1998

Proportionate mortality among union members employed at three Texas refineries.

The cause-specific mortality (1940-1993) of 2,985 male workers employed in three oil refineries was examined using a proportionate mortality study design. Separate analyses were undertaken by race, refinery, employment status (active and retired), and time since entry into the Oil, Chemical, and Atomic Workers (OCAW) union. Proportionate cancer mortality ratio (PCMR) analyses also were conducted. Proportionate mortality ratios (PMR) were significantly increased (P < 0.05) for cancers of the lip (PMR = 384), stomach (PMR = 142), unspecified sites of the liver (PMR = 238), pancreas (PMR = 151), connective tissues (PMR = 243), prostate (PMR = 135), eye (PMR = 407), brain (PMR = 181), benign and unspecified neoplasms (PMR = 289), and leukemia (PMR = 175) for the entire cohort. Significantly decreased mortality was observed for respiratory tuberculosis (PMR = 29), esophageal cancer (PMR = 45), rectal cancer (PMR = 49), and cancers of the bladder and other urinary organs (PMR = 40). Skin cancer was observed to be significantly increased (PMR = 242) for workers with less than 20 years since union initiation. Significantly increased PCMRs were seen for cancers of unspecified sites of the liver (PCMR = 205), brain (PCMR = 147), benign and unspecified neoplasms (PCMR = 243), and leukemia (PCMR = 146). Among nonwhites, an increased risk of bone cancer was observed in the PCMR analysis (PCMR = 704), although based on only two deaths. Analyses of mortality patterns for white males by refinery revealed similar patterns in each refinery as was seen in the overall cohort of refinery workers. Mortality patterns for whites and nonwhites also were similar. Additional analyses of deaths between 1960 and 1993 demonstrated increased mortality due to asbestosis (PMR = 683) and multiple myeloma (PMR = 124), although the multiple myeloma excess was not statistically significant. Ten deaths due to mesotheliomas were observed among these refinery workers.

Adult↗
PubMed1999

Mortality study in an Italian oil refinery: extension of the follow-up.

This article present the results of the extension of the follow-up of a cohort of workers employed in an Italian oil refinery. 1,583 workers employed in 1949-1982 in a northern Italy oil refinery plant were followed-up for mortality as of May 31, 1991. Environmental measurements documented potential exposure to benzene. Standardized mortality ratios (SMR) and their 95% confidence intervals (95% CI) were calculated using as references national (1949-1968) and regional mortality rates (1969-1991). Elevated mortality from lymphoma (seven deaths, SMR 190, 95% CI 76-391) and leukemia (eight deaths, SMR 225, 95% CI 97-443) was observed. No consistent trends by length of employment or time since first exposure were apparent. Nonetheless, the excess risk was particularly and significantly increased among workers with 15 or more years of employment, and 30 or more years since first employment. The findings of elevated mortality from leukemia and lymphoma are in agreement with those of other oil refinery studies. Chance, confounding, or other biases might have played a marginal, if any, role in determining the results. Exposure to benzene is a biologically plausible explanation.

Carcinogens↗