Individual and population exposures to gasoline.

Gasoline is a complex mixture of many constituents in varying proportions. Not only does the composition of whole gasoline vary from company to company and season to season, but it changes over time. The composition of gasoline vapors is dominated by volatile compounds, while "gasoline" in groundwater consists mainly of water-soluble constituents. Hydrocarbons, including alkanes, alkenes, and aromatics, make up the large majority of gasoline, but other substances, such as alcohols, ethers, and additives, may also be present. Given this inability to define "gasoline,h' exposures to individual chemicals or groups of chemicals must be defined in a meaningful exposure assessment. An estimated 111 million people are currently exposed to gasoline constituents in the course of refueling at self-service gasoline stations. Refueling requires only a few minutes per week, accruing to about 100 min per year. During that time, concentrations in air of total hydrocarbons typically fall in the range 20-200 parts per million by volume (ppmV). Concentrations of the aromatic compounds benzene, toluene, and xylene rarely exceed 1 ppmV. Some liquid gasoline is also released, generally as drops less than 0.1 g each, but with enough larger spills to raise the average loss per gallon dispensed to 0.23 g for stations with conventional nozzles and 0.14 g per refueling for stations with vapor recovery nozzles (Stage II controls). Some skin exposure may occur from these spills but the exposure has not been quantified. Two major types of vehicular emissions have been studied. Evaporative emissions include emissions while the vehicle is driven (running losses), emissions after the engine has been shut off but is still warm (hot soak), and emissions during other standing periods (diurnal) emissions. These evaporative emissions are dominated by the more volatile gasoline components. Tailpipe emissions include some unreacted gasoline constituents as well as products of combustion (including chemicals identical to some of the original constituents of the gasoline) and a variety of hydrocarbons and related compounds. Running losses are reported to fall in the range of 0.2 to 2.8 g of total hydrocarbons per mile driven, while benzene evaporative emissions range from 0.002 to 0.007 g/mile. Benzene levels inside travelling vehicles have been reported to average about 13 ppbV in Los Angeles. Tailpipe emissions amount to 0.3 to 1.0 g/mile of total hydrocarbons; emissions of benzene, polycylic aromatic hydrocarbons, and 1,3-butadiene have been reported to range from 0.015 to 0.04 g/mile, 0.00025 to 0.00046 g/mile, and 0.001 to 0.005 g/mile, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)     

Gasoline vapor exposures. Part II. Evaluation of the nephrotoxicity of the major C4/C5 hydrocarbon components

Analysis of workplace exposures to gasoline vapors revealed that C4 and C5 hydrocarbons constitute anywhere from 67 to 74% by weight of a typical vapor. Furthermore, it was found that n-butane, isobutane, n-pentane, and isopentane together comprise greater than 90% of all the C4/C5 vapor components and approximately 61 to 67% by weight of the total vapor. Accordingly, a 21-day inhalation toxicity study of a blend consisting of 25% (w/w) each of these four hydrocarbons was conducted using rats to assess the potential for these major gasoline vapor components to induce kidney damage. No evidence of the kidney lesions typically associated with hydrocarbon-induced nephropathy was observed in rats exposed at up to 11 800 mg/m3 (4437 ppm) of the blend.     

Dangerous and cancer-causing properties of products and chemicals in the oil refining and petrochemical industry. VIII. Health effects of motor fuels: carcinogenicity of gasoline--scientific update.

1. Significant increases in tumors of kidney, liver, and other tissues and organs following exposure to gasoline provide sufficient evidence of carcinogenicity. 2. Benzene, a significant component of gasoline, has been established without question as a human carcinogen by IARC, EPA, and WHO. 3. 1,3-Butadiene, a component of gasoline, is a powerful carcinogen in both animals and humans. 4. Sufficient evidence for the carcinogenicity of alkyl benzenes, very significant components of gasoline, has also been established. 5. Human epidemiologic studies show important increases in cancers of the kidney, stomach, brain, pancreas, prostate, lung, and skin as well as hematopoietic and lymphatic leukemias as a result of exposure to gasoline, its components, and its vapors. 6. Stage 2 controls are being implemented to reduce exposure of the human population to gasoline vapors.     

Estimating the gasoline components and formulations toxicity to microalgae (Tetraselmis chuii) and oyster (Crassostrea rhizophorae) embryos: an approach to minimize environmental pollution risk

Even though petrochemical contamination frequently occurs in the form of oil spills, it is thought that a greater danger to coastal habitats is posed by chronic petrochemical toxicity associated with urban run-off, in which gasoline water-soluble-fraction (WSF) plays an important role. The hypothesis of the entrepreneurs, who were associated to the scientists uncharged of this research, was that recycled petrochemical waste may provide different gasoline formulations, having different toxic properties; the correlation between the gasoline formulations and their components' toxicological effects might contribute to the reformulation of the products, in such a way that the gasoline generated could be less toxic and less harmful to the environment. The aim of this research was to determine the toxic effects of 14 different types of gasoline (formulated, in accordance with National Petroleum Agency standards, from petrochemical waste), on Tetraselmis chuii (microalgae culture) and Crassostrea rhizophorae (embryos). Microalgae and oyster embryos were exposed to different gasoline formulations water-soluble fractions (WSF) at a range of concentrations (0%, 4.6%, 10.0%, 22.0%, 46.0%, and 100%), for 96 and 24h, respectively. The tests were carried out under controlled conditions. End-points have been CI50-96h (concentration causing 50% growth inhibition in microalgae cultures) and EC50-24h (concentration causing abnormalities on 50% of the exposed embryos). Through these procedures, gasoline formulations, which represent the lowest environmental risk, were selected. Bioassays carried out on the 8 different gasoline components aimed to correlate gasoline toxicity with the toxic potential of its components. The analysis of principal components showed that the C9DI, a mixture of aromatic hydrocarbons of 9 carbon atoms, had the highest level of toxic potential, followed by C9S (a mixture of aromatics with 9-11 carbon atoms) and heavy naphtha. The results showed gasoline formulations 1-4 (monoaromatic hydrocarbons being the most conspicuous components) to be the least toxic, whilst formulations 12-14 (having higher content of C9DI, C9S and naphtha) were found to be the most harmful to organisms. This study led to the identification of the most toxic WSF gasoline components (C9DI and C9S), and to the possibility of developing more eco-compatible gasoline formulations.     

Absence of hydrocarbon-induced nephropathy in rats exposed subchronically to volatile hydrocarbon mixtures pertinent to gasoline

Ninety-day inhalation studies were conducted on 50:50 weight percent (wt %) mixtures of n-butane:n-pentane and isobutane:isopentane, respectively, and on a distillation cut boiling below 145 degrees F of a reference unleaded gasoline blend to assess the nephrotoxicity of these volatile mixtures. The mixtures of butanes and pentanes were selected because these four hydrocarbons are the most prevalent components of gasoline vapors encountered under typical occupational exposures. The 0-145 degrees F gasoline distillation fraction was tested because it reasonably approximates the composition of gasoline vapors measured under occupational settings. Male and female F-344 rats were exposed to 2 levels of each mixture, 6 hours per day, 5 days per week, for 13 weeks. The target concentrations for the butane:pentane mixtures were 4500 and 1000 parts per million (ppm), while 5200 and 1200 ppm were set for the gasoline distillation fraction. An interim sacrifice was conducted after 28 days. The rats were not significantly affected by the exposures, and there was no evidence of hydrocarbon-induced nephropathy in either sex at the termination of each study. However, at the 28-day interim sacrifice period for both butane:pentane mixtures, mild, transient treatment-related but not exposure-related kidney effects were observed in the male rats. These perturbations were absent at the interim sacrifice period for the gasoline distillation fraction.     

Customer exposure to gasoline vapors during refueling at service stations

Gasoline is a volatile complex mixture of hydrocarbon compounds that is easily vaporized during handling under normal conditions. Modern reformulated gasoline also contains oxygenates to enhance octane number and reduce ambient pollution. This study measured the difference in the exposure of customers to gasoline and oxygenate vapors during refueling in service stations with and without vapor recovery systems. Field measurements were carried out at two self-service stations. One was equipped with Stage I and the other with Stage II vapor recovery systems. At Stage I stations there is vapor recovery only during delivery from road tanker, and at Stage II stations additional vapor recovery during refueling. The exposure of 20 customers was measured at both stations by collecting air samples from their breathing zone into charcoal tubes during refueling with 95-octane reformulated gasoline. Each sample represented two consecutive refuelings. The samples were analyzed in the laboratory by gas chromatography using mass-selective detection for vapor components. The Raid vapor pressure of gasoline was 70 kPa and an oxygen content 2 wt%. Oxygenated gasoline contained 7 percent methyl tert-butyl ether (MtBE) and 5 percent methyl tert-amyl ether (MtAE). The geometric mean concentrations of hydrocarbons (C3-C11) in the customers' breathing zone was 85 mg/m3 (range 2.5-531 mg/m3) at the Stage I service station and 18 mg/m3 (range < 0.2-129 mg/m3) at the Stage II service station. The geometric mean of the exposure of customers to MtBE during refueling at the Stage I service station was 15.3 mg/m3 (range 1.8-74 mg/m3), and at the Stage II service station 3.4 mg/m3 (range 0.2-16 mg/m3). The differences in exposure were statistically significant (p < 0.05). The mean refueling times were 57 seconds (range 23-207) at the Stage I and 66 seconds (range 18-120) at the Stage II station. The measurements were done on consecutive days at the various service stations. The temperature ranged from 10 to 17 degrees C, and wind velocity was 2-4 m/s. The climatic conditions were very similar on the measurement days. Based on this study it was found that the Stage II vapor recovery system reduces gasoline emission considerably. The exposure level of customers at the Stage II station during refueling was circa 20-25 percent of the exposure at the Stage I service station when conditions were equal and no other confounding factors such as leaks or spills were present.     

Frequency of oral mucosa micronuclei in gas station operators after introducing methanol

Methanol has been proposed in different countries as an alternative automotive fuel to be used as an additive to, or replacement for, gasoline or ethanol. Utilization of methanol is increasing exposure to low levels of methanol vapors in the environment and more specifically in occupational settings such as gas stations. Pump operators are exposed to relatively high levels of fuel vapors, the consequences of which have not been fully examined. In this study, the micronucleus assay in squamous oral cells was performed on pump operators of 28 gas stations in three different periods in the city of S?o Paulo, Brazil. The frequency of micronuclei (MN) was evaluated before and 1 year after a mixed fuel called MEG, which contains 33% methanol, 60% ethanol and 7% gasoline, was introduced. The third evaluation, 3 years later, represents a period where the number of cars using alcohol fuel had decreased drastically and the pump operator exposure to MEG became very low. The frequency of MN observed in 76 employees in 1992 (mean = 3.62 +/- 0.39) was significantly increased (P < 0.001) as compared with 76 operators exposed in 1989 (mean = 1.41 +/- 0.26) and 129 exposed in 1995 (mean = 1.20 +/- 0.15). These differences were also significant when compared with control groups not exposed professionally to motor fuel. These findings could indicate a mutagenic hazard of the MEG occurring in those with occupational exposure.     

Source apportionment of exposure to toxic volatile organic compounds using positive matrix factorization

Data from the Total Exposure Assessment Methodology studies, conducted from 1980 to 1987 in New Jersey (NJ) and California (CA), and the 1990 California Indoor Exposure study were analyzed using positive matrix factorization, a receptor-oriented source apportionment model. Personal exposure and outdoor concentrations of 14 and 17 toxic volatile organic compounds (VOCs) were studied from the NJ and CA data, respectively. Analyzing both the personal exposure and outdoor concentrations made it possible to compare toxic VOCs in outdoor air and exposure resulting from personal activities. Regression analyses of the measured concentrations versus the factor scores were performed to determine the relative contribution of each factor to total exposure concentrations. Activity patterns of the NJ and CA participants were examined to determine whether reported exposures to specific sources correspond to higher estimated contributions from the factor identified with that source. For a subset of VOCs, a preliminary analysis to determine irritancy-based contributions of factors to exposures was carried out. Major source types of toxic VOCs in both NJ and CA appear to be aromatic sources resembling automobile exhaust, gasoline vapor, or environmental tobacco smoke for personal exposures, and automobile exhaust or gasoline vapors for outdoor concentrations.     

Gasoline and vapor exposures in service station and leaking underground storage tank scenarios.

Exposure to gasoline and gasoline vapors from service station operations and leaking underground storage tanks is a major health concern. Six scenarios for human exposure were examined, based primarily on measured air and water concentrations of total hydrocarbons, benzene, xylenes, and toluene. Calculated mean and upper limit lifetime exposures provide a tool for assisting public health officials in assessing and managing gasoline-related health risks.     

Does environmental exposure to manganese pose a health risk to healthy adults?

Manganese is an essential nutrient that also may be toxic at high concentrations. Subjects chronically exposed to manganese-laden dust in industrial settings develop neuropsychological changes that resemble Parkinson's disease. Manganese has been proposed as an additive to gasoline (as a replacement for the catalytic properties of lead), which has generated increased research interest in the possible deleterious effects of environmental exposure to manganese. Low-level exposure to manganese has been implicated in neurologic changes, decreased learning ability in school-aged children, and increased propensity for violence in adults. However, a thorough review of the literature shows very weak cause-and-effect relationships that do not justify concern about environmental exposure to manganese for most of the North American population.     

Carcinogenicity in mice by inhalation of benzotrichloride and benzoyl chloride

Benzotrichloride and benzoyl chloride are suspected to be causative agents of lung cancer and maxillary malignant lymphoma of workers employed in factories producing benzoyl chloride. The present study was undertaken to evaluate the carcinogenicity in mice of inhaling benzotrichloride and benzoyl chloride. Mice inhaled benzotrichloride and benzoyl chloride vapor for 30 min/d for 2 d/wk for 5 months, and each animal was followed for several month without subsequent exposure. Tumor developed in the lung, skin and lymphatic tissues at high incidences in mice inhaling benzotrichloride. By benzotrichloride vaporized at 50 degrees C, the incidence of pulmonary tumors was 53.1% (17/32, p less than 0.001), that of skin tumors was 25% (8/32, p less than 0.02), and that of malignant lymphoma was 25% (8/32, p less than 0.02) observed at the 10th month after exposure. These are significantly higher than that observed in control mice. In mice exposed to benzotrichloride vaporized at room temperature, the incidence of pulmonary tumors was 81.1% (30/37), that of skin tumors was 27.0% (10/37), and that of malignant lymphoma was 10.8% (4/37) observed at the 15th month after exposure. On the other hand, by benzoyl chloride vaporized at 50 degrees C, the incidence of pulmonary tumors was 10.7% (3/28) and that of skin tumors was 7.1% (2/28), but these incidences did not show any significant difference from the controls. These results suggest that the carcinogenicity of benzotrichloride is much higher than benzoyl chloride and that benzotrichloride is the primary cause of malignancies developing among workers engaged in manufacturing benzoyl chloride.     

Factors related to the prevalence of respiratory symptoms in workers in a petrochemical complex

This study was performed to evaluate the prevalence of respiratory symptoms in workers in a petrochemical complex and to elucidate the relationship between the prevalence and work-related factors. A questionnaire was distributed to 5,983 male workers working in a petrochemical complex. As for the respiratory symptoms, cough was present in 2.4%, phlegm in 8.1%, wheezing in 2.8% and shortness of breath in 4.7% of the workers. The factors significantly related to respiratory symptoms were smoking history, wearing of protective devices, handling of substances toxic to the respiratory system, and history of atopy or respiratory disease (p<0.05). The substances toxic to the respiratory system were divided into 4 types, ie., dusts, solvents, metals, and vapors. When the analysis was performed to evaluate the effects of exposure to substance type on respiratory symptoms, the odds ratio of cough was 1.96 times higher in those workers exposed to dusts compared with those not exposed, 2.28 times for exposure to metals, 1.52 times for solvents, and 1.55 times for vapors, all showing significant differences (p<0.05). For phlegm, the odds ratio was 1.08 times higher in those workers exposed to dusts compared with those not exposed, 1.94 times for exposure to metals, 1.70 times for organic solvents, and 1.85 for vapors (p<0.05). For wheezing, the odds ratio was 2.38 times for exposure to dusts; for shortness of breath, it was 2.42 times for exposure to dusts, 2.89 times for metals, 2.10 times for organic solvents, and 2.14 times for vapors, all showing significant differences (p<0.05). In conclusion, work-related factors significantly affected the respiratory symptoms in workers working in the petrochemical complex. Especially, these respiratory symptoms were significantly related to exposure to toxic substances and the wearing of protective devices. Thus, safety education and management are needed for these workers.     

Assessing total exposures to gasoline vapor using the source exposure model.

Recent developments in source apportionment modeling of volatile organic compounds (VOCs) include receptor modeling (RM) applications to "total" (indoor and outdoor) exposure assessment for source of VOC. Source fingerprints are available for major VOC sources such as gasoline vapor, automobile exhaust, refinery emissions, cleaning solvent vapors, printing inks, and waste-water treatment facilities. The relative proportion of each VOC species in the source fingerprint enables the RM method, through a least squares analysis, to identify each source's presence and quantify its contribution to ambient air concentrations. Sampling periods and locations may be selected to represent microenvironmental exposures. Receptor modeling has direct applicability to determining the relative contribution of gasoline vapors to VOC exposures in the general population.     

Measuring exposure to an elemental mercury spill--Dakota County, Minnesota, 2004

Elemental mercury spills can cause contamination of neighborhoods and homes and result in neurologic and kidney disorders in exposed persons who inhale mercury vapors. Often, however, difficulties exist in determining the magnitude of exposure and effectiveness of decontamination or in recognizing that reexposure has occurred. This report summarizes the response to an elemental mercury exposure that resulted in the decontamination of 48 persons and the subsequent analysis of blood and urine samples from 14 exposed youths aged 6-16 years. Data from these analyses suggest that 1) blood samples are more sufficiently acquired and can be used to evaluate recent acute exposure and 2) use of a real-time mercury vapor analyzer can help public health officials determine the magnitude of exposures and help prevent reexposures. In addition, demolition and waste-disposal firms and government agencies must take actions to ensure that elemental mercury is adequately secured before disposal.     

Nested case-control study of leukaemia, multiple myeloma, and kidney cancer in a cohort of petroleum workers exposed to gasoline

OBJECTIVES: This nested case-control study was based on data in a cohort study of more than 18,000 petroleum distribution workers exposed to gasoline, which contains about 2%-3% benzene. Risks of leukaemia, acute myeloid leukaemia, multiple myeloma, and kidney cancer were examined relative to exposure to gasoline. METHODS: For each case, up to five individually matched controls were selected. Analyses based on the Mantel-Haenszel procedure as well as univariate and multivariate conditional logistic regression were performed for each disease category. Jobs with similar exposures were grouped into homogeneous categories for analysis. Several quantitative indices of exposure to gasoline were used in the analyses: duration of exposure, cumulative exposure, frequency of peak exposure, and time of first exposure. RESULTS: No increased risks for the four cancers were found for any job category. Analyses with logistic regression models based on duration of exposure, cumulative exposure, and frequency of peak exposure did not show any increased risk or exposure-effect relation. Time of first exposure to gasoline was also found to be unrelated to the four diseases under investigation. CONCLUSION: Exposure to gasoline or benzene at the concentrations experienced by this cohort of distribution workers is not a risk factor for leukaemia (all cell types), acute myeloid leukaemia, multiple myeloma, or kidney cancer.

 

     

Toxicokinetics of human exposure to methyl tertiary-butyl ether (MTBE) following short-term controlled exposures.

Methyl tertiary-butyl ether (MTBE) is an oxygenated compound added to gasoline to improve air quality as part of the US Federal Clean Air Act. Due to the increasing and widespread use of MTBE and suspected health effects, a controlled, short-term MTBE inhalation exposure kinetics study was conducted using breath and blood analyses to evaluate the metabolic kinetics of MTBE and its metabolite, tertiary-butyl alcohol (TBA), in the human body. In order to simulate common exposure situations such as gasoline pumping, subjects were exposed to vapors from MTBE in gasoline rather than pure MTBE. Six subjects (three females, three males) were exposed to 1.7 ppm of MTBE generated by vaporizing 15 LV% MTBE gasoline mixture for 15 min. The mean percentage of MTBE absorbed was 65.8 +/- 5.6% following exposures to MTBE. The mean accumulated percentages expired through inhalation for 1 and 8 h after exposure for all subjects were 40.1% and 69.4%, respectively. The three elimination half-lives of the triphasic exponential breath decay curves for the first compartment was 1-4 min, for the second compartment 9-53 min, and for the third compartment 2-8 h. The half-lives data set for the breath second and blood first compartments suggested that the second breath compartment rather than the first breath compartment is associated with a blood compartment. Possible locations for the very short breath half-life observed are in the lungs or mucous membranes. The third compartment calculated for the blood data represent the vessel poor tissues or adipose tissues. A strong correlation between blood MTBE and breath MTBE was found with mean blood-to-breath ratio of 23.5. The peak blood TBA levels occurred after the MTBE peak concentration and reached the highest levels around 2-4 h after exposures. Following the exposures, immediate increases in MTBE urinary excretion rates were observed with lags in the TBA excretion rate. The TBA concentrations reached their highest levels around 6-8 h, and then gradually returned to background levels around 20 h after exposure. Approximately 0.7-1.5% of the inhaled MTBE dose was excreted as unchange urinary MTBE, and 1-3% was excreted as unconjugated urinary TBA within 24 h after exposure.     

Elevated risk for male breast cancer after occupational exposure to gasoline and vehicular combustion products

BACKGROUND: Automotive gasoline contains benzene, 1,3-butadiene, 1, 2-dibromoethane and 1,2-dichloroethane, and the combustion products include certain polycyclic aromatic hydrocarbons, all of which have shown mammary gland carcinogenicity in long-term bioassays. It is the aim of this paper to investigate whether men occupationally exposed to gasoline and its combustion products have an elevated risk of breast cancer. METHODS: A nationwide register based case control study on male breast cancer morbidity was established among members of a pension fund, compulsory for all employees. Employment histories were reconstructed for each of 230 cases and 12,880 control subjects based on computerized records. The odds ratios, adjusted for socioeconomic status, were estimated by conditional logistic regression analysis. RESULTS: When a lag time of at least 10 years was included, the odds ratio for breast cancer among men with over three months of employment in trades with potential exposure to gasoline and combustion products was 2.5 (95% confidence interval: 1.3-4.5). Among men younger than 40 years at the time of first employment, the odds ratio was 5.4 (2.4-11.9). CONCLUSIONS: This study supports the hypothesis that occupational exposure to gasoline vapors and combustion products may play a role in the causation of male breast cancer. This hypothesis warrants further evaluation particularly in women.     

Pulmonary fibrosis in cable plant workers exposed to mist and vapor of petroleum distillates

Twenty-five cable plant workers exposed to mists and vapors of mineral oils and kerosene for 5-35 years have been investigated in a cross-sectional, matched pairs study. The exposed cohort and the referents were examined by radiology, pulmonary function measurements, and a questionnaire for symptoms of respiratory disease. Lung tissue from a deceased worker with 35 years of exposure was investigated by histopathologic methods and by scanning electron microscopy. Exposure measurements were performed by personal sampling. Previous employment and smoking habits were recorded for all subjects. An increased prevalence of slight basal lung fibrosis was found in chest films of the exposed workers. Pulmonary fibrosis was confirmed histopathologically. A moderately decreased vital capacity (VC) and forced expiratory volume (FEV1) was found. Oil mist was measured to time-weighted average levels of 0.15-0.30 mg/m3 with short-term vapor exposure of up to 4000 mg/m3. It is concluded that mists and vapors from petroleum distillates are the most probable causes of the findings.     

More human, more humane: a new approach for testing airborne pollutants

People not only inhale airborne contaminants but also absorb them through the skin. Both routes can set off localized toxic reactions or damage internal organs such as the liver, kidney, and brain. Conventional tests of the toxicity of gases and vapors, in which laboratory animals are exposed to lethal or sub-lethal doses of chemicals, have been criticized as expensive, unethical, inhumane, and time-consuming. Now researchers at the University of New South Wales (UNSW) in Sydney, Australia, have developed an animal-free alternative that uses human cells to test the effects of exposure to airborne toxicants.     

Effect of waste anesthetic gas and vapor exposure on reproductive outcome in veterinary personnel

Elevated rates of adverse reproductive outcome among medical and dental personnel exposed to waste anesthetic gas and vapor have been noted in the literature. NIOSH issued recommended standards for occupational exposure to these agents in a criteria document published in 1977. This study was designed to investigate adverse reproductive outcome in veterinary personnel who are exposed to waste anesthetic gas and vapors at levels near the NIOSH recommended standards. This epidemiologic study employed case-control methodology using a national sample of male veterinarians, female veterinarians and female veterinary assistants. Occupational exposure to waste anesthetic gas and vapors was not found to be associated significantly with adverse reproductive outcome at the 95% confidence level for female veterinary personnel when adjustment was made for use of diagnostic x-rays. Use of diagnostic x-rays in veterinary practice was associated with a statistically significant increase in odds ratios for spontaneous abortion in female veterinarians and veterinary assistants.