Biomedical subjects

E A Eisen

Publications and source records attributed to E A Eisen.

At least 19 recordsLinked to original sources

PubMed2006

DNA adducts among asphalt paving workers.

OBJECTIVE: Asphalt is used extensively in the highway construction industry and contains a complex mixture of polycyclic aromatic hydrocarbons, some of which are known or suspected to be human carcinogens. Though numerous epidemiologic studies have described an excess cancer risk among asphalt workers, a causal relationship has not been established. Accordingly, the primary objective of this study was to use DNA adducts as a biomarker of biologically effective dose and determine whether DNA damage resulted from occupational exposure to asphalt among paving workers. METHODS: Over a 12 month period, four peripheral blood samples (spring, summer, fall and winter) were obtained from 49 asphalt paving workers (169 samples) and 36 non-paving construction workers (103 samples). The spring, summer and fall samples were collected during the work-season, whereas the winter samples were collected during the off-season (due to the seasonality of paving work). Mononuclear white blood cells were isolated and analyzed for DNA adducts via the (32)P-postlabeling assay and generalized linear models were used to evaluate the DNA adduct data. RESULTS: Among paving workers during the work-season, DNA adducts increased during each day of the workweek such that mean adduct levels were lowest on Mondays (3 adducts per 10(10) nucleotides) and highest on Fridays (46 adducts per 10(10) nucleotides). Additionally, a 3-fold difference in adduct burden was observed by paving task such that mean adduct levels were lowest among roller operators (7 adducts per 10(10) nucleotides) and highest among screedmen (23 adducts per 10(10) nucleotides). Using adducts as a measure of biologically effective dose, these findings (weekday trend and task-based differences) were consistent with a previous evaluation of absorbed dose in the same population. Adduct levels were not, however, higher among paving workers than among non-pavers. Adducts were also highest during the winter months, suggestive of a seasonal effect that has been observed in previous studies. CONCLUSION: These findings indicate that adduct burden increased throughout the workweek among paving workers, suggesting that DNA damage may be associated with occupational exposure to hot-mix asphalt. However, the lack of contrast with non-paving workers, as well as the seasonal variation warrants additional investigation.

Air Pollutants, Occupational↗

PubMed2005

A 20-year follow-up study on chronic respiratory effects of exposure to cotton dust.

In order to evaluate chronic effects of long-term exposure to cotton dust on respiratory health, and the role of dust and endotoxin, longitudinal changes in lung function and respiratory symptoms were observed prospectively from 1981 to 2001 in 447 cotton textile workers, along with 472 silk textile controls. The results from five surveys conducted over the 20-yr period are reported, including standardised questionnaires, pre- and post-shift spirometric measurements, work-area inhalable dust sample collections and airborne Gram-bacterial endotoxin analysis. Cotton workers had more persistent respiratory symptoms and greater annual declines in forced expiratory volume in one second (FEV1) and forced vital capacity as compared with silk workers. After exposure cessation, in the final 5-yr period, the rate of FEV1 decline tended to slow in nonsmoking males, but not in nonsmoking females. Workers who reported byssinotic symptoms more persistently suffered greater declines in FEV1. Chronic loss in lung function was more strongly associated with exposure to endotoxin than to dust. In conclusion, the current study suggests that long-term exposure to cotton dust, in which airborne endotoxin appears to play an important role, results in substantial adverse chronic respiratory effects.

Byssinosis↗

PubMed2004

Inhalation and dermal exposure among asphalt paving workers.

The primary objective of this study was to identify determinants of inhalation and dermal exposure to polycyclic aromatic compounds (PACs) among asphalt paving workers. The study population included three groups of highway construction workers: 20 asphalt paving workers, as well as 12 millers and 6 roadside construction workers who did not work with hot-mix asphalt. During multiple consecutive work shifts, personal air samples were collected from each worker's breathing zone using a Teflon filter and cassette holder connected in series with an XAD-2 sorbent tube, while dermal patch samples were collected from the underside of each worker's wrist. All exposure samples were analyzed for PACs, pyrene and benzo[a]pyrene. Inhalation and dermal PAC exposures were highest among asphalt paving workers. Among paving workers, inhalation and dermal PAC exposures varied significantly by task, crew, recycled asphalt product (RAP) and work rate (inhalation only). Asphalt mix containing high RAP was associated with a 5-fold increase in inhalation PAC exposures and a 2-fold increase in dermal PAC exposure, compared with low RAP mix. The inhalation PAC exposures were consistent with the workers' proximity to the primary source of asphalt fume (paver operators > screedmen > rakers > roller operators), such that the adjusted mean exposures among paver operators (5.0 microg/m3, low RAP; 24 microg/m3, high RAP) were 12 times higher than among roller operators (0.4 microg/m3, low RAP; 2.0 microg/m3, high RAP). The dermal PAC exposures were consistent with the degree to which the workers have actual contact with asphalt-contaminated surfaces (rakers > screedmen > paver operators > roller operators), such that the adjusted mean exposures among rakers (175 ng/cm2, low RAP; 417 ng/cm2, high RAP) were approximately 6 times higher than among roller operators (27 ng/cm2, low RAP; 65 ng/cm2, high RAP). Paving task, RAP content and crew were also found to be significant determinants of inhalation and dermal exposure to pyrene. The effect of RAP content, as well as the fact that exposures were higher among paving workers than among millers and roadside construction workers, suggests that the PAC and pyrene exposures experienced by these paving workers were asphalt-related.

Construction Materials↗

PubMed2004

Urinary 1-hydroxypyrene and polycyclic aromatic hydrocarbon exposure among asphalt paving workers.

OBJECTIVES: Using urinary 1-hydroxypyrene (1-OHP) as a measure of total absorbed dose, the primary objective of this study was to evaluate the total effect of inhalation and dermal PAH exposures while considering other factors such as age, body mass index and smoking that may also have a significant effect on urinary 1-OHP. METHODS: The study population included two groups of highway construction workers: 20 paving workers and 6 milling workers. During multiple consecutive workshifts, personal air and dermal samples were collected from each worker and analyzed for pyrene. During the same work week, urine samples were collected pre-shift, post-shift and at bedtime each day and analyzed for 1-OHP. Distributed lag models were used to evaluate the independent effect of inhalation and dermal exposures that occurred at each of several preceding exposure periods and were used to identify the relevant period of influence for each pathway. RESULTS: The paving workers had inhalation (mean 0.3 micro g/m(3)) and dermal (5.7 ng/cm(2)) exposures to pyrene that were significantly higher than the milling workers. At pre-shift on Monday morning, following a weekend away from work, the pavers and millers had the same mean baseline urinary 1-OHP level of 0.4 micro g/g creatinine. The mean urinary 1-OHP levels among pavers increased significantly from pre-shift to post-shift during each work day, while the mean urinary 1-OHP levels among millers varied little and remained near the baseline level throughout the study period. Among pavers there was a clear increase in the pre-shift data during the work week, such that the average pre-shift level on day 4 (1.4 micro g/g creatinine) was 3.5 times higher than the average pre-shift results on day 1 (0.4 micro g/g creatinine). The results of the distributed lag model indicated that the impact of dermal exposure was approximately eight times the impact of inhalation exposure. Furthermore, dermal exposure that occurred during the preceding 32 h had a statistically significant effect on urinary 1-OHP, while the effect of inhalation exposure was not significant. CONCLUSIONS: We found that distributed lag models are a valuable tool for analyzing longitudinal biomarker data and our results indicate that dermal contact is the primary route of exposure to PAHs among asphalt paving workers. An exposure assessment of PAHs that does not consider dermal exposure may considerably underestimate cumulative exposure and control strategies aimed at reducing occupational exposure to asphalt-related PAHs should include an effort to reduce dermal exposure.

Air Pollutants, Occupational↗

PubMed2004

A case-crossover study of transient risk factors for occupational acute hand injury.

BACKGROUND: Workers with acute hand injuries account for over 1 000 000 emergency department visits annually in the United States. AIMS: To determine potential transient risk factors for occupational acute hand injury. METHODS: Subjects were recruited from 23 occupational health clinics in five northeastern states in the USA. In a telephone interview, subjects were asked to report the occurrence of seven potential risk factors within a 90-minute time period before an acute hand injury. Each case also provided control information on exposures during the month before the injury. The self-matched feature of the study design controlled for stable between-person confounders. RESULTS: A total of 1166 subjects were interviewed (891 men, 275 women), with a mean age (SD) of 37.2 years (11.4). The median time interval between injury and interview was 1.3 days. Sixty three per cent of subjects had a laceration. The relative risk of a hand injury was increased when working with equipment, tools, or work pieces not performing as expected (11.0, 95% CI 9.4 to 12.8), or when using a different work method to do a task (10.5, 95% CI 8.7 to 12.7). Other transient factors in decreasing order of relative risk were doing an unusual task, being distracted, and being rushed. Wearing gloves reduced the relative risk by 60% (0.4, 95% CI 0.3 to 0.5). Occupational category, job experience, and safety training were found to alter several of these effects. CONCLUSION: The results suggest the importance of these transient, potentially modifiable factors in the aetiology of acute hand injury at work. Attempts to modify these exposures by various strategies may reduce the incidence of acute hand injury at work.

Accidents, Occupational↗

PubMed2004

Risk of upper aerodigestive tract cancers in a case-cohort study of autoworkers exposed to metalworking fluids.

AIMS: To re-examine aerodigestive cancer risk in a cohort of autoworkers exposed to metal working fluids (MWF), using improved case definition and more recently diagnosed cases. METHODS: The autoworker cohort included 31 100 hourly workers alive on 1 January 1985 who worked at three automobile plants in Michigan. A case-cohort design was carried out that included incident cases of cancers of the larynx, oesophagus, and stomach, and a 10% sample of the cohort. A Cox proportional hazards model was used to estimate MWF exposure effects. The smoothing method of penalised splines was used to explore the shape of the underlying exposure-response curves. RESULTS: The most important finding was the association between larynx cancer incidence and cumulative straight MWF exposure. The results for oesophageal cancer were less consistent. For stomach cancer there was no evidence of excess risk. CONCLUSION: This association between larynx cancer and straight MWF exposures was consistent with a previous finding in this cohort, providing further support for a causal relation.

Aged↗

PubMed2004

Smoothing in occupational cohort studies: an illustration based on penalised splines.

AIMS: To illustrate the contribution of smoothing methods to modelling exposure-response data, Cox models with penalised splines were used to reanalyse lung cancer risk in a cohort of workers exposed to silica in California's diatomaceous earth industry. To encourage application of this approach, computer code is provided. METHODS: Relying on graphic plots of hazard ratios as smooth functions of exposure, the sensitivity of the curve to amount of smoothing, length of the exposure lag, and the influence of the highest exposures was evaluated. Trimming and data transformations were used to down-weight influential observations. RESULTS: The estimated hazard ratio increased steeply with cumulative silica exposure before flattening and then declining over the sparser regions of exposure. The curve was sensitive to changes in degrees of freedom, but insensitive to the number or location of knots. As the length of lag increased, so did the maximum hazard ratio, but the shape was similar. Deleting the two highest exposed subjects eliminated the top half of the range and allowed the hazard ratio to continue to rise. The shape of the splines suggested a parametric model with log hazard as a linear function of log transformed exposure would fit well. CONCLUSIONS: This flexible statistical approach reduces the dependence on a priori assumptions, while pointing to a suitable parametric model if one exists. In the absence of an appropriate parametric form, however, splines can provide exposure-response information useful for aetiological research and public health intervention.

Adult↗

PubMed2003

Respiratory symptoms and cotton dust exposure; results of a 15 year follow up observation.

AIMS: To determine chronic effects of long term exposure to cotton dust and endotoxin on incidence of respiratory symptoms and the effect of cessation of exposure. METHODS: Respiratory health in 429 Chinese cotton textile workers (study group) and 449 silk textile workers (control group) was followed prospectively from 1981 to 1996. Byssinosis, chest tightness, and non-specific respiratory symptoms were assessed by means of identical standardised questionnaires at four time points. Exposures to cotton dust and endotoxin were estimated using area samples collected at each survey. Incidence and persistence of symptoms were examined in relation to cumulative exposure and exposure cessation using generalised estimating equations (GEE). RESULTS: Among cotton workers, the cumulative incidence of byssinosis and chest tightness was 24% and 23%, respectively, and was significantly more common in smokers than in non-smokers. A high proportion of symptoms was found to be intermittent, rather than persistent. Among silk workers, no typical byssinosis was identified; the incidence of chest tightness was 10%. Chronic bronchitis, cough, and dyspnoea were more common and persistent in the cotton group than in the silk group. Significantly lower odds ratios for symptoms were observed in cotton workers who left the cotton mills; risk was also related to years since last worked. Multivariate analysis indicated a trend for higher cumulative exposure to endotoxin in relation to a higher risk for byssinosis. CONCLUSION: Chronic exposure to cotton dust is related to both work specific and non-specific respiratory symptoms. Byssinosis is more strongly associated with exposure to endotoxin than to dust. Cessation of exposure may improve the respiratory health of cotton textile workers; the improvement appears to increase with time since last exposure.

Adult↗

PubMed2001

A case-crossover study of occupational traumatic hand injury: methods and initial findings.

BACKGROUND: Acute hand injury is the leading cause of occupational injury treated in United States' hospital emergency departments (e.g., laceration, crush or fracture). To identify risk factors for traumatic hand injuries, we conducted a case-crossover study of transient exposures (e.g., being rushed) for acute occupational traumatic hand injury. METHODS: The case-crossover method, which uses subjects as their own controls, was used to identify risk factors for occupational hand injury. Two hundred and thirty-two subjects were recruited from 17 occupational health clinics in New England and interviewed by telephone a median of 1.2 days after their injury. The a priori hazard period was defined as 10 min before the injury. Two control periods were used: one was 60-70 min prior to the injury (matched-pair interval analysis); the other was the total work-time exposed, on average, in the previous month (usual frequency analysis). RESULTS: In the usual frequency analysis, the relative risk for using malfunctioning or different-from-usual equipment or tools in the hazard period was 25.5 (95% confidence interval = 18.4-35.2). Relative risks were also significantly elevated for performing a task using an unusual work method, doing an unusual task, being distracted, or being rushed. Wearing gloves appeared to be protective (relative risk = 0.8, 95% CI = 0.5-1.2). Matched-pair interval analysis, where appropriate, provided similar findings but had much wider confidence intervals. CONCLUSIONS: This study demonstrates that the case-crossover design is a feasible and efficient method for studying transient risk factors for sudden-onset traumatic occupational hand injury. The usual frequency analysis proved more useful than the match-pair approach to control period selection.

Accidents, Occupational↗

PubMed2001

Respiratory health of automobile workers and exposures to metal-working fluid aerosols: lung spirometry.

BACKGROUND: Despite substantial evidence that workers exposed to metal-working fluids (MWF) have increased respiratory morbidity, the few studies of chronic effects on lung function have not been conclusive. METHODS: Lung spirometry was measured and both current and past exposures to metal-working fluid (MWF) aerosols were estimated in this cross-sectional cohort of 1,811 male automobile workers. Satisfactory exposure data were available for 1,745 (96%): 239 assemblers (never-exposed to MWF), 487 assemblers (previously exposed), 352 machinists currently exposed to straight oils, 441 to soluble oils, and 226 to synthetic fluids. Operations were classified as either grinding or non-grinding machining. RESULTS: Current exposure was not found to be associated with either forced expiratory volume in 1 second (FEV(1)) or forced ventilatory capacity (FVC). Nor was past exposure to water-based fluids (soluble or synthetic MWF) related to pulmonary function. Past exposure to straight oils, however, was significantly associated with FVC. This association was more obvious among older workers and among workers who had never transferred from MWF exposed jobs to assembly. CONCLUSIONS: The magnitude of the association between FVC and lifetime exposure to straight MWF was slightly larger than the estimated cigarette effect, suggesting that the impact of an additional year of exposure to 1 mg/m(3) of mineral oil particulate in the thoracic particle size range, has the same impact on FVC as smoking one pack per day for one more year.

Adult↗

PubMed2001

A prospective study of lung function among boilermaker construction workers exposed to combustion particulates.

BACKGROUND: Given the evidence of both acute cross-shift and short-term decrements in lung function in boilermaker construction workers following occupational exposure to combustion particulates, we sought to determine whether exposure is associated with an annual loss in lung function. METHODS: As part of an ongoing investigation, we conducted a 2-year longitudinal study of lung function among 118 boilermakers. Exposure was assessed with a work history questionnaire. Spirometry measurements were performed annually. RESULTS: We found an association between annual FEV(1) and hours worked at a gas-fired plant during the previous year, beta = - 9.8 mls/100 hours worked (95% CI: - 16.0, - 3.5) after adjustment for age, baseline FEV(1) and cigarette smoking status. The adjusted association between FEV(1) and "ever" worked at a gas-fired plant was - 99.7 mls (95% CI: - 154.8, - 44.5). There was also evidence of a negative association between FEV(1) and "ever" worked and hours worked at oil and coal-fired plants. CONCLUSIONS: These data suggest an association between annual lung function loss and working at gas, coal and oil-fired plants. Further follow-up of this cohort of boilermakers is in progress.

Adult↗

PubMed2001

Subclinical immunologic and physiologic responses in hexamethylene diisocyanate-exposed auto body shop workers.

BACKGROUND: Diisocyanates are potent sensitizing agents and currently the most commonly identified cause of occupational asthma in industrialized countries. However, diisocyanate asthma is difficult to diagnose and exposure and host risk factors are unclear. Auto body shops, one of the most common hexamethylene diisocyanate (HDI) exposure settings, are particularly difficult to study due to their small size and episodic exposures. Surveillance studies of such workers are limited. OBJECTIVES: We have initiated a cross-sectional field epidemiologic study, Survey of Painters and Repairers of Auto bodies by Yale (SPRAY), to characterize the effects of diisocyanate exposures on actively employed auto body shop workers. Methods and Results We present here questionnaire, physiologic, immunologic, and exposure data on 75 subjects enrolled in the study. No overt cases of clinically apparent diisocyanate asthma were identified based on spirometry, methacholine challenge, peak flows, and symptoms. HDI-specific lymphocyte proliferation was present in 30% of HDI-exposed workers and HDI-specific IgG in 34% of HDI-exposed workers, but they were not associated. HDI-specific IgE was detected in two workers. HDI-specific lymphocyte proliferation, increased methacholine responsiveness, and symptoms of chest tightness and shortness of breath were more common in the most heavily HDI-exposed workers, the painters. More long-term follow-up of this cohort should clarify the significance of these HDI-specific immunologic responses, physiologic changes, and symptoms. CONCLUSIONS: These findings demonstrate the presence of HDI-specific immune responses in a large proportion of healthy HDI-exposed workers.

Adolescent↗

PubMed2001

Longitudinal changes in pulmonary function and respiratory symptoms in cotton textile workers. A 15-yr follow-up study.

To evaluate the chronic effects of exposure to cotton dust, a 15-yr follow-up study in cotton textile workers was performed in Shanghai, China from 1981 to 1996. Testing occurred four times during the 15-yr period. The achieved follow-up rates were 76-88% of the original 447 cotton textile workers, and 70-85% of the original 472 silk textile workers (as a control group). Identical questionnaires, equipment, and methods were used throughout the study. The prevalence of byssinosis increased over time in cotton workers, with 15.3% at the last survey versus 7.6% at the baseline, whereas no byssinosis was found in silk workers. More workers in the cotton group consistently reported symptoms than in the silk group, although symptom reporting varied considerably from survey to survey. Cotton workers had small, but significantly greater, adjusted annual declines in FEV(1) and FVC than did the silk workers. Years worked in cotton mills, high level of exposure to endotoxin, and across-shift drops in FEV(1) were found to be significant determinants for longitudinal change in FEV(1), after controlling for appropriate confounders. Furthermore, there were statistically significant associations between excessive loss of FEV(1) and byssinosis, chest tightness at work, and chronic bronchitis in cotton workers. Workers who consistently (three or four of the surveys) reported byssinosis or chest tightness at work had a significantly greater 15-yr loss of FEV(1). We conclude that long-term exposure to cotton dust is associated with chronic or permanent obstructive impairments. Consistent reporting of respiratory symptoms, including byssinosis and chest tightness at work, is of value to predict the magnitude and severity of chronic impairments in textile workers.

Adult↗

PubMed2001

Exposure-response models based on extended follow-up of a cohort mortality study in the automobile industry.

OBJECTIVE: This report describes the extended follow-up of a cohort of 46 399 automobile manufacturing workers with potential exposure to metalworking fluids (MWF). The outcomes of interest were cancers of the esophagus, stomach, colon, rectum, liver, pancreas, larynx, skin, prostate, and brain, as well as leukemia. Additional follow-up increased the power to detect modest elevations in mortality rates in association with specific types of MWF, including synthetic fluids not in widespread use until the 1970s. METHODS: Standardized mortality ratios (SMR) were computed for the most recent 10 years of follow-up, as well as for the entire study period. Adjusted relative risks (RR) were estimated in Poisson regression models with categorical variables for cumulative exposure to each type of MWF and in proportional hazards models with continuous exposure variables. RESULTS: Associations were found between straight MWF and esophageal, laryngeal and rectal cancer; soluble MWF and cancer of the esophagus, larynx, skin, and brain; synthetic MWF and cancer of the esophagus, liver, and prostate. The elevated RR values were modest in magnitude (1.5 to 2.0). SMR values were increased for stomach, liver, and pancreatic cancer and also for leukemia in the last 10 years of follow-up. The SMR values were also elevated for stomach and liver cancer among the persons recently hired. CONCLUSIONS: The results provide further evidence that exposure to metalworking fluids causes cancer among workers in automobile manufacturing. Although airborne exposures declined over the study period, this study suggests that modest risk of several digestive cancers, as well as prostatic cancer and leukemia, may persist at current levels of exposure to water-based metalworking fluids.

Automobiles↗

PubMed2000

Implications of different fiber measures for epidemiologic studies of man-made vitreous fibers.

BACKGROUND: Several researchers have proposed fiber size ranges representing hypotheses about the biological activity of fibers. Each of these indices has a biologically plausible rationale, yet they propose different fiber dimensions. METHODS: Four biologically based and one standard fiber analytic method index, the NIOSH 7400 method with B rules, were evaluated in air monitoring data collected in a variety of fiber glass (FG) manufacturing settings to determine their impact on an assessment of fiber exposure for an epidemiologic study of the risk of respiratory cancer among FG production workers. RESULTS: All indices varied considerably within and among the range of fiber size distributions sampled in the FG factories. CONCLUSIONS: The asymptotic relative efficiencies (R(2)) calculated among the five indices indicate a potentially important loss of power from the use of the standard method index, if one of the biologically based indices is more closely related to the disease outcome in an epidemiologic study.

Epidemiologic Methods↗

PubMed1999

Cotton dust and endotoxin exposure and long-term decline in lung function: results of a longitudinal study.

BACKGROUND: To evaluate the relationship between long-term exposure to cotton dust and Gram-negative bacterial endotoxin on lung function, we conducted an 11-year follow-up study of cotton textile workers in Shanghai, China. METHODS: Workers at a nearby silk-thread manufacturing mill were used as a referent population. Ninety percent of the original cohort of 445 cotton and 467 silk textile workers--both active and retired--were identified for testing in the 11th year. Questionnaires and spirometric testing were performed, as well as cotton dust and endotoxin sampling at three points over the 11-year follow-up period: at baseline, at Year 5, and at Year 11. After excluding deaths and subjects on sick-leave, 84% of the original cohort had complete health and environmental data. RESULTS: The data were reanalyzed using generalized estimating equations feedback model which allow for subject transfer over time between work areas, various exposure levels to dust and endotoxin, and FEV1. Cotton workers had a larger loss of FEV1 during the first 5 years of study (-40 mls/yr) as compared with the second 6 years of follow-up (-18 mls/yr). During the same periods, the average decline among silk workers was slightly higher in the first period, but was more consistent (-30 mls/yr vs. -27 mls/yr), and these differences could not be explained by worker selection or dropout. When cumulative exposure to dust and endotoxin were estimated and used in a multivariate model (GEE) for FEV1 loss, cumulative dust, but not endotoxin, was associated with 11-year loss in FEV1 after adjustments for confounders. There was evidence of feedback between dust-exposure levels and FEV1, indicating the existence of a healthy-worker survivor effect. After accounting for a healthy-worker survivor effect, we found a significant relationship between dust exposure and FEV1 decline. CONCLUSIONS: Our results suggest that cotton dust is more strongly associated with chronic airflow limitation than associated endotoxins. Further work is needed to clarify potential reversibility after cessation of exposure, and the relative contributions of dust, endotoxin, and tobacco to chronic respiratory impairment in cotton and other vegetable-exposed workers.

Case-Control Studies↗

PubMed1999

Methodology for analyzing episodic events.

Many health outcomes of interest to occupational epidemiologists are common recurrent health events. Epidemiologic approaches to the study of such health events are reviewed. Episodic events are considered to be events that occur at a distinct point in time - either with sudden onset or the sudden crossing of a threshold of detection - and they must be reversible events that can recur in the same person in response to a proximate trigger. Studying such health events poses 4 challenges to existing methods: (i) key epidemiologic concepts, such as incidence, do not naturally accommodate recurrent events, (ii) study designs must capture time-varying exposures, (iii) statistical models must be able to handle correlated outcomes, and (iv) feedback bias must be addressed. In response, methods such as longitudinal studies, case-crossover designs and generalized estimating equations are identified as appropriate tools.

Acute Disease↗

PubMed1998

Mortality studies of metalworking fluid exposure in the automobile industry: VI. A case-control study of esophageal cancer.

BACKGROUND: Results are reported from a nested case-control study of 60 esophageal cancer deaths among 46,384 automobile manufacturing workers potentially exposed to metalworking fluids (MWF) in machining and grinding operations. METHODS: By using incidence-density sampling, controls were selected with a sampling ratio of 20:1 from among co-workers who remained at risk by the age of death of the case, matched on race, gender, plant, and year of birth. Conditional logistic regression was used to evaluate the risk associated with cumulative exposure (mg/m3-years) to each of three types of metalworking fluid (straight, soluble, and synthetic MWF), as well as with years of exposure to selected components of MWF, including nitrosamines, sulfur, biocides, and several metals. RESULTS: Esophageal cancer was found to be significantly associated with exposure to both soluble and synthetic MWF in grinding operations. The odds ratios (ORs) for grinding with soluble MWF were elevated at 2.5 or greater in all categories of cumulative exposure, although the exposure-response trend was statistically significant only when exposure was measured as duration. Those with 12 or more years exposure to soluble MWF in grinding operations experienced a 9.3-fold relative risk of esophageal cancer mortality (95% CI = 2.1-42.1). The OR for ever grinding with synthetic MWF was 4.1 (95% CI = 1.1-15.0). Elevated risk was also associated with two agents found in both synthetic and soluble fluids, nitrosamines, and biocides. For exposure to nitrosamines, the OR was 5.4 (95% CI = 1.5-19.9); for biocides the OR was 3.8 (95% CI = 0.8-18.9). However, because the same workers were exposed to grinding with synthetics, nitrosamines and biocides, it was not possible to separate the specific risks associated with these components.

Automobiles↗