Biomedical subjects

S K Hammond

Publications and source records attributed to S K Hammond.

At least 37 records · Page 2Linked to original sources

PubMed1997

Mortality studies of machining fluid exposure in the automobile industry. V: A case-control study of pancreatic cancer.

Results are presented from a case-control study of 97 cases of pancreatic cancer nested in a cohort of workers from three automobile manufacturing plants. Risk was examined for lifetime exposure to straight, soluble, and synthetic metalworking fluids, as used in specific machining or grinding operations, as well as for constituents of the fluids. Pancreatic cancer was associated with exposure to synthetic fluids in grinding operations, with an odds ratio of 3.0 (95% CI: 1.2-7.5) among those with more than 1.4 mg/m3-years of exposure. We were unable to examine synthetic exposure in the absence of grinding because there was virtually no exposure to synthetics in machining operations in this study population. Although a disproportionately high percent of the cases were black, no black workers had any exposure to synthetic fluids, and no other measured exposure was found to be related to risk. Thus, the previously documented excess risk of pancreatic cancer among blacks in this cohort remains unexplained.

Adult↗

PubMed1996

Endotoxin exposure-response in a fiberglass manufacturing facility.

Peak expiratory flow (PEF) and workplace exposure to endotoxin, phenolic resin, and formaldehyde were measured to investigate asthma symptoms and medication use among employees in a fiberglass wool manufacturing plant. Self-recorded PEF was obtained from 37 workers, for a total of 181 days off work and 187 days at work with concurrent personal exposure monitoring. Pre- and post-shift spirometry were obtained on at least 2 days. The 8 hr time-weighted average personal exposure ranges were endotoxin; 0.4-759 ng/m3; phenolic resin, 5.7-327 micrograms/m3; and formaldehyde, 1.2-265 micrograms/m3. Amplitude percent mean peak flow was associated with years since starting regular work in the highest endotoxin exposure area, although current assignment in that area was associated with reduced amplitude--evidence for a healthy worker effect. Exposure-response was analyzed by regression of lung function change on exposure using generalized estimating equations with robust variance estimates. Endotoxin exposure above 4 ng/m3 (8 hr time-weighted average) was associated with a decline in lung function across the work shift, and with drops in lung function 16-20 hr after exposure. Phenolic resin exposure was not consistently associated with decrements, and formaldehyde was not associated with decrements in lung function.

Adult↗

PubMed1996

Validity of surrogates for determination of 30-1000 Hz magnetic field exposure for video display terminal users in office settings.

In studies investigating adverse reproductive outcomes associated with video display terminal (VDT) usage, amounts of time spent in front of a VDT or magnetic field (MF) levels in front of the VDT are used as surrogate measures of subject's MF exposure. However, the relevance of such surrogates to actual exposures has not been demonstrated, and the validity of the use of such measures as a surrogate for the actual MF exposure is only speculative. This study examines 1) measurements of MFs at frequencies of approximately 30-1000 Hz at a fixed distance from the VDTs, 2) reported hours of VDT use, and 3) reported distance between the VDT and the subject's waist as surrogate measures for the average MF exposure level of a VDT user during one 8 h workday. The results showed a weak correlation between the average exposure level of a VDT user and the MF 46 cm from a VDT (R = 0.52, n = 67, P < 0.001). This study showed no association between self-reported hours of VDT usage, or self-reported distance between waist and VDT, and the average MF exposures. Moreover, individuals' average MF exposures did not seem to be affected by other variables, such as position of a VDT on the desk, hours of desk use, and the VDT type (color vs. monochrome). These findings indicate that VDT exposures within office settings are complex and cannot be easily predicted by surrogates.

Computer Terminals↗

PubMed1996

Exposure assessment for a field investigation of the acute respiratory effects of metalworking fluids. I. Summary of findings.

The exposure assessment summarized here is part of an epidemiologic study of the acute respiratory health effects of metalworking fluid (MF) exposures. Exposures were measured as the inhalable concentrations of the MF aerosol, a variety of metals and elements, and endotoxin as well as the level of culturable bacteria in the aerosol size fraction less than 8 microns. Bulk samples of soluble MFs were tested for pH, mineral and tramp oil fraction, endotoxin, culturable bacteria, and lipopolysaccharide levels. The MF exposed workers had higher geometric mean inhalable aerosol exposures (0.181 mg/m3) than the MF unexposed workers (0.046 mg/m3). The MF exposed workers had higher geometric mean (GM) airborne culturable microbial counts (102 colony-forming units (CFU)/m3 for bacteria < 8 microns) than the unexposed workers (GM = 14 CFU/m3). Among the unexposed, Bacillus was the predominant airborne species, while among the exposed workers, Pseudomonas predominated. Exposed workers also had higher geometric mean airborne endotoxin levels (GM = 7.1 endotoxin units (EU)/m3) than the unexposed workers (GM = 1.9 EU/m3). Elemental concentrations of iron, chlorine, and sulfur were substantially higher among the exposed workers compared to the unexposed workers. For soluble metalworking fluids, the levels of bulk constituents were examined by three categories of time since the machine sump was refilled with fresh MF (< 4 days, 4-21 days, > 21 days). Univariate analyses of percent oil, pH, culturable bacteria, tramp oil percent, endotoxin, or fatty acid levels all showed no statistically significant changes in level over time.

Acute Disease↗

PubMed1996

Exposure in a household using gasoline-contaminated water.

Contamination of drinking water with petroleum products is an increasingly common problem. Physicians are often asked to advise patients about such exposures. This study assessed household exposure from gasoline-contaminated drinking water in a New England household. A sampling strategy was designed to estimate inhalation and ingestion exposure to benzene and three other aromatic hydrocarbons typically found in gasoline-contaminated water. The estimated inhaled doses of all agents were similar to the estimated ingested dose. Over half the inhaled dose of all four agents was associated with shower activities as was over half the estimated total dose by all routes of exposure. Under these conditions, discontinuing ingestion of water contaminated with these agents may decrease the dose of benzene by less than one third, whereas discontinuing both ingestion and showering may decrease the dose of benzene by over three quarters. This limited study suggests that routes of exposure other than ingestion are important and should receive attention in the regulatory and risk-assessment process.

Air Pollution, Indoor↗

PubMed1995

Measurement of exposure to environmental tobacco smoke in pregnant women.

The authors compared three methods used to measure exposure to environmental tobacco smoke in pregnant women: personal air monitor, urine cotinine, and questionnaire. Environmental tobacco smoke exposure assessment methods were compared for agreement using Cohen's Kappa and the Spearman rank order correlation coefficient. Women who reported exposure had significantly higher levels of air nicotine concentration compared with women who reported no exposure, but urine cotinine did not differ. Air nicotine was more highly correlated with home exposure (r = 0.34) than work exposure (r = 0.18). Urine cotinine correlated with work exposure (r = 0.14) but neither home nor social exposure. Agreement was "fair" (Kappa = 0.29) when self-reported exposure was compared with air monitor, but agreement was "poor" when urine cotinine was compared with self-report (Kappa = 0.08) and air monitor (Kappa = 0.10). In low environmental tobacco smoke exposure environments, all three methods for measuring exposure may have a role, although modification to monitoring protocols will be needed to improve monitoring sensitivity and exposure classification.

Adult↗

PubMed1995

Occupational exposure to environmental tobacco smoke.

OBJECTIVES: To measure occupational exposures to environmental tobacco smoke in diverse settings, including offices and production areas, and to evaluate the effectiveness of policies that restrict or ban smoking in the workplace. DESIGN: Survey. The average weekly concentration of environmental tobacco smoke was measured with passive monitors that sample nicotine. Approximately 25 samples were placed in each worksite for 1 week. SETTING: Twenty-five Massachusetts worksites, including fire stations, newspaper publishers, textile dyeing plants, and manufacturers of valves, fiberoptics, flight instruments, batteries, adhesives, semiconductor equipment, filters, and tools and dies. Samples were collected in offices and production areas. MAIN OUTCOME MEASURES: The distribution of nicotine concentrations in various work settings as a function of company smoking policy. These data were interpreted with three approaches: comparing measured concentrations with a published risk assessment; comparing occupational exposures with home exposures; and evaluating the "cigarette equivalents" to which workers were exposed. RESULTS: Worksite smoking policy had a major effect on the nicotine concentrations, which fell from a median of 8.6 micrograms/m3 in the open offices at worksites that allowed smoking to 1.3 micrograms/m3 in sites that restricted smoking, and to 0.3 microgram/m3 in worksites that banned smoking. The nonoffice workspaces were affected similarly, with median concentrations of 2.3, 0.7, and 0.2 microgram/m3 at worksites that allowed, restricted, and banned smoking, respectively. CONCLUSION: All three evaluation methods indicated that occupational exposure to environmental tobacco smoke presents a substantial risk to workers in the absence of a policy restricting or banning smoking.

Housing↗

PubMed1995

Association of spontaneous abortion and other reproductive effects with work in the semiconductor industry.

This study tested the hypothesis that fabrication room (fab) work in the silicon-based semiconductor industry is associated with an increased risk of spontaneous abortion (SAB). The study was conducted nationwide at 14 companies representing a spectrum of large to small manufacturers. A small increase in risk of SAB was observed among fab workers compared with nonfabrication room (nonfab) workers in two cohorts, historical (adjusted RR = 1.43, 95% confidence interval [CI] 0.95-2.09) and prospective (adjusted RR = 1.25, 95% CI = 0.63-1.76). Analysis of specific fab exposures in the historical cohort showed a consistent, dose-response association of SAB with photoresist and developer solvents, whose major component was ethylene-based glycol ethers. The consistency of our findings and the toxicological data for these agents suggest that this is a causal association. Independent associations of SAB with self-reported stress and with etching fluorides were observed and require further research. No significant decrease in fertility was observed among men or women working in fabs, but reduced fecundability was suggested for some women fab workers.

Abortion, Spontaneous↗

PubMed1995

Tiered exposure-assessment strategy in the Semiconductor Health Study.

The Semiconductor Health Study included 14 U.S. companies with 82 silicon-based wafer-fabrication rooms and a complex array of processes and chemicals. Its epidemiologic components were a historical examination of spontaneous abortion rates among 902 women, a prospective evaluation of reproductive outcomes in 483 women, and a cross-sectional review of male fertility and of respiratory, ergonomic, neurologic, or gastrointestinal problems among 3,175 men and women. Designing an exposure assessment strategy presented unique problems, and multiple agents had to be evaluated. A three-tiered approach to exposure assessment was developed to reflect increasing specificity of exposures. At the first tier, employees were divided into fabrication and nonfabrication groups. At the second tier, work groups with qualitatively different exposures were determined. At the third tier, intensity of exposures to specific chemical, physical, and ergonomic agents was evaluated. Evaluations were based on worker reports of tasks performed, moderated by fabrication-specific factors observed by study industrial hygienists during site visits.

Data Collection↗

PubMed1995

Patterns of chemical use and exposure control in the Semiconductor Health Study.

Information on chemical use and exposure control between 1986 and 1990 was collected from 14 companies participating in the Semiconductor Health Study. Questionnaires and site visits provided data used to develop exposure categories for three epidemiological studies: prospective, historical, and cross-sectional. Patterns of use of target chemicals were compiled for 82 silicon-wafer fabrication rooms (fabs), including 47 from which subjects were selected for study. Chemical use was examined by operation, year, and epidemiological component. Target agents for epidemiological analyses were present in more than 50% of fabs. Use of these agents was fairly constant from 1986 to 1990, except for a moderate increase in use of propylene glycol monomethyl ether acetate, a solvent being substituted for ethylene-based glycol ethers (EGE) in photoresists. The distribution of personal protective equipment, engineering controls, and other factors potentially affecting employee exposure was also examined. Controls designed to manage processes or high acute toxicity were present in most fabs; their prevalence remained unchanged from 1986 through 1990. Controls designed to reduce exposures to chemicals with low acute toxicity were less widely distributed; their prevalence increased moderately from 1986 to 1990.

Drug-Related Side Effects and Adverse Reactions↗

PubMed1995

Algorithms for estimating personal exposures to chemical agents in the Semiconductor Health Study.

For exposure assessment in a series of epidemiologic studies of semiconductor industry workers, estimates of potential personal exposures to selected chemical agents were developed using a set of algorithms. A worker's total exposure to each agent was defined as the sum of task scores for each task using that agent. Task scores were calculated as the intensity and frequency score for each task, modified by a factor indicating degree of presence of the target agent and a process-specific emission factor representing degree of emission control present for that process. The algorithms used multiple sources of information to generate an exposure score for each worker-process-agent combination. Exposure scores were then placed into ordinal categories of exposure (0-3) for use in the epidemiologic analysis.

Algorithms↗

PubMed1995

Hierarchical cluster analysis for exposure assessment of workers in the Semiconductor Health Study.

The fabrication of integrated circuits in the semiconductor industry involves worker exposures to multiple chemical and physical agents. The potential for a high degree of correlation among exposure variables was of concern in the Semiconductor Health Study. Hierarchical cluster analysis was used to identify groups or "clusters" of correlated variables. Several variations of hierarchical cluster analysis were performed on 14 chemical and physical agents, using exposure data on 882 subjects from the historical cohort of the epidemiological studies. Similarity between agent pairs was determined by calculating two metrics of dissimilarity, and hierarchical trees were constructed using three clustering methods. Among subjects exposed to ethylene-based glycol ethers (EGE), xylene, or n-butyl acetate (nBA), 83% were exposed to EGE and xylene, 86% to EGE and nBA, and 94% to xylene and nBA, suggesting that exposures to EGE, xylene, and nBA were highly correlated. A high correlation was also found for subjects exposed to boron and phosphorus (80%). The trees also revealed cluster groups containing agents associated with work-group exposure categories developed for the epidemiologic analyses.

Cluster Analysis↗

PubMed1995

A model for assessing occupational exposure to extremely low-frequency magnetic fields in fabrication rooms in the Semiconductor Health Study.

A model was created to assess occupational exposure to extremely low-frequency magnetic fields (ELF-MF) among semiconductor fabrication-room (fab) workers. This model was based on the assumption that each subject's exposure arose from being near identifiable ELF-MF sources or being in areas with high ELF-MF levels. To assess ELF-MF exposures, the model superimposed subjects' time-activity patterns (patterns of how and where they spent their time) with measurements of magnetic-field levels from devices and work areas. This model, which was validated by personal dosimetry on 192 persons in three fabs, predicted actual time-weighted average exposures with a correlation coefficient of 0.62. The inability of the model to predict individual exposures more accurately was attributed to unforseen sources of elevated ELF-MF (transformers, distribution panels, sources in adjacent rooms) or to errors in subjects' judgments of time spent near devices. These unpredictable errors are intrinsic to the method used to estimate exposure.

Electromagnetic Fields↗

PubMed1995

Historical cohort investigation of spontaneous abortion in the Semiconductor Health Study: epidemiologic methods and analyses of risk in fabrication overall and in fabrication work groups.

The risk of spontaneous abortion (SAB) in the semiconductor industry was examined in a historical cohort study of pregnancies at 14 companies. We identified female employees who had worked for at least 6 months and whose ages ranged from 18 to 44 years during the 1986-1989 study period. Using company records, we included all fabrication-room (fab) employees and an approximately equal number of nonfabrication (nonfab) employees, for a total sample of 7,269. Telephone interviews with 6,088 women (84%) identified 904 eligible pregnancies and 113 SABs. Exposure classification was based on questionnaire and industrial hygiene assessments of tasks the women performed during the first trimester of pregnancy. Using logistic regression to control for age, smoking, ethnicity, education, income, year of pregnancy, and stress, we found a higher risk of SAB in fab employees than in nonfab employees (15.0% of fab pregnancies ended in SAB vs. 10.4% of nonfab pregnancies, adjusted relative risk [RR] = 1.43, 95% CI = 0.95-2.09). Analysis of fab work groups showed that the highest relative risk was in masking employees (17.5% SAB rate, adjusted RR = 1.78, 95% CI = 1.17-2.62 in comparison with nonfab employees). Within masking, the highest risk was found in etching-related process employees (22.2% SAB rate, adjusted RR = 2.08, 95% CI = 1.27-3.19 in comparison to nonfab employees.

Abortion, Spontaneous↗

PubMed1995

Historical cohort study of spontaneous abortion among fabrication workers in the Semiconductor Health Study: agent-level analysis.

Risk of spontaneous abortion (SAB) was examined in relation to chemical and physical agents in a retrospective study of employees of 14 seminconductor manufacturers: After screening over 6,000 employees, 506 current and 385 former workers were eligible. If a woman had multiple eligible pregnancies, one was selected at random. Telephone interviews provided data on demographics and occupational and other exposures during the first trimester. Two groups of chemicals accounted for the 45% excess risk of SAB among fabrication-room (fab) workers: photoresist and developed solvents (PDS), including glycol ethers, and fluoride compounds used in etching. Women exposed to high levels of both these agents were at greater risk (RR = 3.21, 95% confidence interval [CI] = 1.29-5.96). In fab workers without these exposures, SAB rates were not elevated (adjusted relative risk [RR] = 0.98, 95% CI = 0.55-1.69). An association was seen with workplace stress, which was not limited to women exposed to PDS or fluoride, nor did stress explain the associations between these chemicals and SAB.

Abortion, Spontaneous↗

PubMed1995

Prospectively assessed menstrual cycle characteristics in female wafer-fabrication and nonfabrication semiconductor employees.

Women aged 18-44 years in silicon-wafer fabrication-room (fab) jobs and frequency-matched women in nonfab jobs were screened for a prospective study of reproductive health (n = 2,639). Among the 739 (28%) eligible women, 481 (65%) completed a baseline interview; 402 completed at least one menstrual cycle of follow-up with daily diaries and urinary assays to exclude conceptive cycles. Adjusted mean cycle lengths (MCL) did not differ between fab and nonfab women (p = 0.97). Women working in thin film and ion implantation (TFII) had the highest adjusted MCL (34.8 +/- 1.7 days) compared with nonfab workers (32.5 +/- 1.4 days, p = 0.07). Among women working exclusively in one group, TFII women had significantly higher MCL (36.1 +/- 2.04 days) than nonfab women (32.0 +/- 1.38 days, p = 0.017). TFII women were also more likely to have all cycles > 35 days (adjusted relative risk [RR] = 2.45; 95% CI = 0.85-6.06). Variability was assessed by logarithmic transformation of the mean standard deviation (MLSD) in cycle length per woman and adjusted for age and ethnicity (4.5 days for fab vs. 4.0 days for nonfab, p = 0.16). Women working exclusively in TFII or photolithography (PHOTO) had significantly higher adjusted MLSD in cycle length (6.68 +/- 1.28 and 5.72 +/- 1.24 days, respectively) than women in nonfab (4.1 +/- 1.16 days, p = 0.013 and 0.019, respectively). Fab and nonfab women did not differ significantly in mean days of bleeding or risk of having cycles > 35 or < 24 days. However, elevated risks of having cycles < 24 days were seen in supervisor engineers (adjusted RR = 2.46, 95% CI = 1.19-3.63) and PHOTO women (adjusted RR = 1.83, 95% CI = 0.94-2.88).

Adolescent↗

PubMed1995

Prospective assessment of fecundability of female semiconductor workers.

To investigate a possible effect of reduced fecundability (probability of conception per menstrual cycle) among women who fabricate silicon wafers, 152 fabrication-room (fab) and 251 nonfab workers were followed for an average of five menstrual cycles. Daily urine samples were analyzed to confirm clinical spontaneous abortions (SABs) and early fetal losses (EFLs). Adjusted fecundability odds ratios (FRs) for fab workers ranged from 0.59 to 0.72 (p = 0.09-0.28 vs. nonfab). For clinical pregnancies only, the adjusted FR ranged from 0.43-0.50 (p = 0.04-0.09 vs. nonfab). This lower fecundability was most pronounced among dopants and thin-film workers [adjusted FR = 0.61, 95% confidence interval (CI) = 0.27-1.40 for all pregnancies; adjusted FR = 0.22, 95% CI = 0.05-0.96 for clinical pregnancies] and in workers exposed to ethylene-based glycol ethers (adjusted FR = 0.37, 95% CI = 0.11-1.19).

Abortion, Spontaneous↗

PubMed1995

Prospective monitoring of early fetal loss and clinical spontaneous abortion among female semiconductor workers.

Women who work in silicon wafer fabrication rooms (fabs) have been reported to have an increased risk of spontaneous abortion (SAB). Although previous studies have included only clinically recognized SABs, more than two-thirds of SABs may be clinically unrecognized. To determine whether fab work is associated with SAB, we recruited 152 fab and 251 nonfab workers, who collected urine samples for a 6-month period. Samples were analyzed by immunoradiometric assay for the presence of human chorionic gonadotropin to detect early fetal losses. Approximately 63% of fab and 46% of nonfab pregnancies ended in SAB [adjusted relative risk (RR) = 1.25; 95% confidence interval (CI) = 0.63-1.76]. Similar RR were seen for women who worked in dopant and thin-film processes (adjusted RR = 1.30; 95% CI = 0.51-1.96) or in masking (adjusted RR = 1.30; 95% CI = 0.59-1.84). The four pregnancies among women who worked with ethylene-based glycol ethers ended in SAB.

Abortion, Spontaneous↗