Hematopoietic and lymphatic malignancies in vehicle mechanics

Reduced Haematopoietic Output in Automobile Mechanics and Sprayers with Chronic Exposure to Petrochemicals: A Case-Control Study in Cape Coast, Ghana

Background

Automobile mechanics and sprayers are at a higher risk of exposure to hazardous chemicals such as polycyclic aromatic hydrocarbons and heavy metals which may cause adverse health outcomes. This study aimed to use reticulocyte count as an indirect measure of the haematological output in automobile mechanics and sprayers in the Cape Coast Metropolis, Ghana.

Method

This cross-sectional study recruited 130 participants: 90 cases (57 automobile mechanics and 33 automobile sprayers) and 40 controls (nonautomobile workers). Venous blood samples were drawn from the participants and examined for full blood count and absolute reticulocyte count. Semi-structured questionnaire was used to collect demographic and occupational safety information from participants.

Results

75.6% of cases had never received occupational safety training. Whereas 35.1% of automobile mechanics routinely siphoned fuel, 36.4% of automobile sprayers never used nose masks in the discharge of their duties. Controls had significantly higher WBC counts compared to mechanics (p = 0.0001; 5.04 ± 1.7 versus 3.81 ± 1.1), or sprayers (p = 0.0004; 5.04 ± 1.7 versus 3.74 ± 0.9). Lymphocyte, monocyte, and platelet counts were also significantly higher in controls compared to cases. Whereas RBC counts were significantly higher in controls compared to automobile mechanics (4.85 versus 4.66; p = 0.034), haemoglobin levels were significantly higher in automobile sprayers compared to controls (15.13 versus 14.1 g/dl; p = 0.0126). Absolute reticulocyte count was significantly higher in controls compared to cases [p < 0.0001; (56.88 ± 32.14) × 10⁹/L (controls) versus (25.31 ± 15.75) × 10⁹/L (sprayers) or (33.27 ± 24.42) × 10⁹/L (mechanics)]. Among the cases however, only RBC counts were significantly lower in automobile mechanics compared to automobile sprayers (p = 0.0088; 4.66 ± 0.4 versus 4.85 ± 0.5).

Conclusion

It was evident that both automobile mechanics and sprayers had significantly reduced haematopoietic output. Occupational safety training is not given priority and must be addressed.

Benzene Exposures and Risk Potential for Vehicle Mechanics from Gasoline and Petroleum-Derived Products

Benzene exposures among vehicle mechanics in the United States and abroad were characterized using available data from published and unpublished studies. In the United States, the time-weighted-average (TWA) airborne concentration of benzene for vehicle mechanics averaged 0.01-0.05 ppm since at least the late 1970s, with maximal TWA concentrations ranging from 0.03 to 0.38 ppm. Benzene exposures were notably lower in the summer than winter and in the Southwest compared to other geographic regions, but significantly higher during known gasoline-related tasks such as draining a gas tank or changing a fuel pump or fuel filter. Measured airborne concentrations of benzene were also generally greater for vehicle mechanics in other countries, likely due to the higher benzene content of gasoline and other factors. Short-term airborne concentrations of benzene frequently exceeded 1 ppm during gasoline-related tasks, but remained below 0.2 ppm for tasks involving other petroleum-derived products such as carburetor and brake cleaner or parts washer solvent. Application of a two-zone mathematical model using reasonable input values from the literature yielded predicted task-based benzene concentrations during gasoline and aerosol spray cleaner scenarios similar to those measured for vehicle mechanics during these types of tasks. When evaluated using appropriate biomarkers, dermal exposures were found to contribute little to total benzene exposures for this occupational group. Available data suggest that vehicle mechanics have not experienced significant exposures to benzene in the workplace, except perhaps during short-duration gasoline-related tasks, and full-shift benzene exposures have remained well below current and contemporaneous occupational exposure limits. These findings are consistent with epidemiology studies of vehicle mechanics, which have not demonstrated an increased risk of benzene-induced health effects in this cohort of workers. Data and information presented here may be used to assess past, current, or future exposures and risks to benzene for vehicle mechanics who may be exposed to gasoline or other petroleum-derived products.

Exposure of petrol station attendants and auto mechanics to premium motor sprit fumes in Calabar, Nigeria

A population-based-cross-sectional survey was carried out to investigate the potential risk of exposure to premium motor spirit (PMS) fumes in Calabar, Nigeria, among Automobile Mechanics (AM), Petrol Station Attendants (PSA) and the general population. Structured questionnaire was administered on the randomly chosen subjects to elicit information on their exposure to PMS. Duration of exposure was taken as the length of work in their various occupations. Venous blood was taken for methaemoglobin (MetHb) and packed cells volume (PCV). Mean MetHb value was higher in AM (7.3%) and PSA (5.8%) than in the subjects from the general population (2.7%). PCV was lower in PSA (30.8%), than AM (33.3%) and the subjects from the general population (40.8%). MetHb level was directly proportional, and PCV inversely related, to the duration of exposure. The study suggested increased exposure to petrol fumes among AM, PSA, and MetHb as a useful biomarker in determining the level of exposure to benzene in petrol vapour.

Personal exposure to benzene from fuel emissions among commercial fishers: comparison of two-stroke, four-stroke and diesel engines

Commercial fishers are exposed to unburned hydrocarbon vapors and combustion products present in the emissions from their boat engines. The objective of this study was to measure personal exposure to benzene as a marker of fuel exposure, and to predict exposure levels across categories of carbureted two-stroke, four-stroke and diesel engines. A self-monitoring approach, employing passive monitors, was used to obtain measurements of personal exposure to benzene over time. Mixed-effect linear regression models were used to predict exposure levels, identify significant effects and determine restricted maximum likelihood estimates for within- and between-person variance components. Significant fixed effects for engine type and refueling a car or truck were identified. After controlling for refueling, predicted benzene exposure levels to fishers on boats equipped with two-stroke, four-stroke and diesel engines were 58.4, 38.9 and 15.7 microg/m3, respectively. The logged within-person variance component was 1.43, larger than the between-person variance component of 1.13, indicating that the total variation may be attributable to monitor placement, environmental conditions and other factors that change over time as well as differences between individual work practices. The health consequences of exposure to marine engine emissions are not known. The predicted levels are well below those at which health effects have been attributed, however.

Etiology of acute myeloid leukemia in the elderly

The biologic and epidemiologic study of acute myeloid leukaemia (AML) in the elderly is in its infancy. Most epidemiologic data attempting to ascertain the etiology of AML have been obtained from younger cohorts or patients with therapy-related AML. The increasing prevalence of deletional and complex karyotypes in elderly AML patients implies a cumulative genotoxicity over time for this subgroup, given the similar spectrum of abnormalities following exposure to known genotoxic agents such as alkylating chemotherapeutic drugs. Exposure to benzene, radiation, and tobacco smoke are clear but weak risk factors for AML. Polymorphic variants in several genes responsible for genomic protection and integrity are now also weak risk factors for AML. Future epidemiologic studies should correlate exposure data with well-defined biologic subtypes of AML.

Lymphohaematopoietic cancer risk among chemical workers exposed to benzene

AIMS

To determine cause specific mortality in a cohort of 2266 chemical workers exposed to benzene in various manufacturing processes after 1935.

METHODS

The cohort has accumulated over 80 000 person-years of observation; about 70% of the workers were followed for more than 30 years since first exposure.

RESULTS

Mortality from non-malignant diseases of the blood was increased (SMR 2.17, 95% CI 0.87 to 4.48), and correlated with duration of benzene exposure, although risk had decreased from the previous investigation of this cohort. The risk for leukaemia was slightly above background (SMR 1.14, obs 12, 95% CI 0.59 to 1.99) but has also decreased since the earlier study of this cohort. SMRs for acute non-lymphocytic leukaemia (ANLL), chronic lymphatic leukaemia, and non-Hodgkin's lymphoma were 1.11, 0.42, and 1.06 respectively. There was evidence of a weak trend of increasing SMRs for leukaemia and possibly ANLL with increasing low-level cumulative exposure but not with other measures.

CONCLUSION

Leukaemia and ANLL results were consistent with the mildly increased risk estimates from lower exposure subgroups of the Pliofilm cohort.

Environmental and biological monitoring of benzene during self-service automobile refueling

Although automobile refueling represents the major source of benzene exposure among the nonsmoking public, few data are available regarding such exposures and the associated uptake of benzene. We repeatedly measured benzene exposure and uptake (via benzene in exhaled breath) among 39 self-service customers using self-administered monitoring, a technique rarely used to obtain measurements from the general public (130 sets of measurements were obtained). Benzene exposures averaged 2.9 mg/m(3) (SD = 5.8 mg/m(3); median duration = 3 min) with a range of < 0.076-36 mg/m(3), and postexposure breath levels averaged 160 microg/m(3) (SD = 260 microg/m(3)) with a range of < 3.2-1,400 microg/m(3). Log-transformed exposures and breath levels were significantly correlated (r = 0.77, p < 0.0001). We used mixed-effects statistical models to gauge the relative influences of environmental and subject-specific factors on benzene exposure and breath levels and to investigate the importance of various covariates obtained by questionnaire. Model fitting yielded three significant predictors of benzene exposure, namely, fuel octane grade (p = 0.0011), duration of exposure (p = 0.0054), and season of the year (p = 0.032). Likewise, another model yielded three significant predictors of benzene concentration in breath, specifically, benzene exposure (p = 0.0001), preexposure breath concentration (p = 0.0008), and duration of exposure (p = 0.038). Variability in benzene concentrations was remarkable, with 95% of the estimated values falling within a 274-fold range, and was comprised entirely of the within-person component of variance (representing exposures of the same subject at different times of refueling). The corresponding range for benzene concentrations in breath was 41-fold and was comprised primarily of the within-person variance component (74% of the total variance). Our results indicate that environmental rather than interindividual differences are primarily responsible for benzene exposure and uptake during automobile refueling. The study also demonstrates that self-administered monitoring can be efficiently used to measure environmental exposures and biomarkers among the general public.

Acute myeloid leukaemia and exposure to organic solvents--a case-control study

The objective was to study the relation between exposure to organic solvents and the risk of developing acute myeloid leukaemia (AML) in Caucasians aged 18 years and more. Ninety-eight cases of AML were diagnosed from September 1986 to March 1990 in Novi Sad, Yugoslavia, and in two London hospitals from September 1988 and May 1994 and from July 1992 and July 1994, respectively. Two controls were matched to each case by hospital, year of admission, gender and 5-year age group. Information on solvent exposure was collected by interview. Odds ratios (ORs) were derived with conditional logistic regression. The degree of solvent exposure was determined by three experts blind to the status of the subject with good agreement between them (the kappa coefficient ranged between 0.52 and 0.86). The response rate for cases was 80%. Exposure to solvents was associated with the increased risk of AML (OR: 2.52; 95% CI: 1.45-4.39; p = 0.001) and those with probable exposure to solvents were found to have an odds ratio of AML over three times greater than non-exposed. We also found an elevated OR for exposure to oils (OR: 1.56) but this was not statistically significant. There is no clear pattern of increasing risks with increasing duration of employment but a significant risk was found for exposures of 10 years or less. An induction period of less than 10 years or more than 30 years was associated with a significantly raised OR. There was a significant excess of machinery mechanics and fitters among the cases.