Cancer Mortality Among US Workers Employed in Semiconductor Wafer Fabrication

Biomonitoring of Exposures to Solvents and Metals in Electronics Manufacturing Facilities in Batam, Indonesia

Concerns about chemical exposure in the electronics manufacturing industry have long been recognized, but data are lacking in Southeast Asia. We conducted a study in Batam, Indonesia, to evaluate chemical exposures in electronics facilities, using participatory research and biological monitoring approaches. A convenience sample of 36 workers (28 exposed, 8 controls) was recruited, and urine samples were collected before and after shifts. Five solvents (acetone, methyl ethyl ketone, toluene, benzene, and xylenes) were found in 46%-97% of samples, and seven metals (arsenic, cadmium, cobalt, tin, antimony, lead, and vanadium) were detected in 60%-100% of samples. Biological monitoring and participatory research appeared to be useful in assessing workers' exposure when workplace air monitoring is not feasible due to a lack of cooperation from the employer. Several logistical challenges need to be addressed in future biomonitoring studies of electronics workers in Asia in factories where employers are reluctant to track workers' exposure and health.

Lymphohematopoietic cancer mortality among Korean semiconductor manufacturing workers

BACKGROUND

We aimed to examine the lymphohematopoietic cancer mortality in a cohort of workers at a semiconductor manufacturing company in South Korea according to their jobs.

METHODS

A retrospective cohort was constructed using the personnel records of semiconductor manufacturing workers who were employed in a semiconductor company in South Korea in 1998-2012. Data on their vital status and causes of death were obtained from the National Statistical Office of South Korea. The standardized mortality ratios (SMRs) of lymphohematopoietic cancer were calculated.

RESULTS

A total of 288 deaths were reported, of which 22 were caused by lymphohematopoietic cancer, among 65,782 workers in 878,325 person-years. The SMRs for lymphohematopoietic cancer were 0.78 (95% confidence interval [CI] = 0.39-1.40; the number of observed cases [Obs] = 11) among male workers and 1.71 (95% CI = 0.85-3.06; Obs = 11) among female workers. Among female operators, excess deaths due to lymphohematopoietic cancer (SMR = 2.59, 95% CI = 1.24-4.76) and leukemia (SMR = 2.92, 95% CI = 1.26-5.76) were observed. However, they were not observed among office workers, facility managers, utility managers, or process managers.

CONCLUSION

Female operators involved in the semiconductor wafer fabrication process had higher risk of mortality from lymphohematopoietic cancer.

Semiconductor Work, Leukemia, and Cancer Risk: A Systematic Review and Meta-Analysis

BACKGROUND

With the development of the semiconductor industry over the past 60 years, various occupational diseases have been reported to coincide with rapid industrial growth. Among these occupational diseases, the association between semiconductor work and cancers, including leukemia, remains controversial. Therefore, this systematic review and meta-analysis assesses the associations between semiconductor work, leukemia, and cancer risk.

METHODS

The core research databases, including PubMed, were screened for studies published until 31 July 2022. All eligible studies assessed cancer risk among workers in the semiconductor industry.

RESULTS

Nine studies were selected after a literature review. The employment period of semiconductor workers in each study was between 1965 and 2009. Semiconductor work was not significantly associated with the risk of leukemia (Relative Risk [RR], 1.02; 95% Confidence Interval [CI], 0.74-1.41) or cancer (RR, 1.00; 95% CI, 0.93-1.07).

CONCLUSION

In this meta-analysis, semiconductor work was not significantly associated with leukemia or cancer risk. Internal comparisons, such as non-fab workers, quality of the study, employment period, and healthy worker effect, should be considered for interpretation. Furthermore, a prospective cohort study based on overall semiconductor workers in the industry could be useful to assess occupational disease risk as a mandatory component of health assessment.

Biological Assessment of Potential Exposure to Occupational Substances in Current Semiconductor Workers with at Least 5 Years of Employment

Background: this study aimed to conduct a biological assessment of the potential exposure to carcinogenic substances in current semiconductor workers. Methods: A cross-sectional study was conducted on 306 semiconductor workers. The assessed biomarkers were as follows: (benzene) urine S-phenylmercapturic, trans,trans-muconic acid, blood benzene; (trichloroethylene) urine trichloroacetic acid; (2-ethoxyethanol) 2-ethoxyacetic acid; (arsine) urine arsenic3+, arsenic5+, monomethylarsonic, dimethylarsinic acid, arsenobetaine; (shift work) 6-hydroxymelatonin; (smoking) cotinine, and (radiation). The detection rate of these materials is defined as more than the biological exposure index (BEI) or the previous reference value. Results: Some workers exposed to trans,trans-muconic acid, trichloroacetic acid, and arsenic5+ showed high BEI levels. Generally, there was no difference according to job categories, and workers were suspected to be exposed to other sources. The melatonin concentration tended to decrease when working at night, and cotinine was identified as an excellent surrogate marker for smoking. In the case of radiation exposure, there was no significant difference in the number of stable chromosome translocation in 19 semiconductor workers. Their estimated radiation exposure level was below the limit of detection (LOD) or near the LOD level. Conclusion: In this study, most carcinogens were below the BEI level, but verification through re-measurement was needed for workers who were identified to have a high BEI level. For continuous monitoring, a prospective cohort is necessary to deal with the healthy worker effect and assess additional materials.

Two Semiconductor Companies' Financial Support Compensation (FSC) Programs for Semiconductor Workers with Suspected Work-Related Diseases (WRDs)

This study described two companies’ financial compensation programs for semiconductor workers with suspected work-related diseases (WRDs) and discussed the major related issues. The key contents of the programs found on the websites opened by two semiconductor companies (Samsung and SK Hynix) were cited. In order to select the suspected WRDs for the FSC, all available epidemiologic studies related to health problems conducted in the semiconductor industry were reviewed. Most program contents are similar, although the amount of financial compensation and a few types of disease available for compensation differ between the companies. The group of cancer, rare disease, childhood rare disease among children born to semiconductor workers (hereafter selected diseases among offspring), and fetal loss, including spontaneous abortion (SAB) and stillbirth, were considered for compensation. An employment duration of longer than one year on a semiconductor production line is required for FSC for cancer or rare disease. The FSC for SAB and offspring disease require a period of employment longer than one month, either before three months prior to conception or between conception and childbirth. The maximum amount of compensation per type of cancer and rare disease was fixed based on the medical treatment fee. The FSC programs of the two companies have been operated successfully to date. These programs are arguably considered to contribute to resolving the conflict between companies and workers with WRDs.

A comparison of meta-analysis results with and without adjustment for the healthy worker effect: cancer mortality among workers in the semiconductor industry

OBJECTIVES

This study compared the results of meta-analysis with and without adjustment for the healthy worker effect on the association between working in the semiconductor industry and cancer mortality.

METHODS

Six studies that reported standardized mortality ratios (SMRs) for cancers were selected for meta-analysis. Using a random-effects model, the SMR results from each study were combined for all cancers and leukemias to estimate the summary SMRs (95% confidence interval, CI). To adjust for the healthy worker effect, the relative standardized mortality ratio (rSMR=SMRx/SMRnot x) were calculated using observed and expected counts for the specific cause of interest (i.e., all cancers and leukemias) and the observed and expected counts for all other causes of mortality. Then, the rSMR results were combined to estimate the summary rSMRs (95% CIs).

RESULTS

The SMRs for all causes of mortality among semiconductor industry workers ranged from 0.25 to 0.80, which reflects a significant healthy worker effect. A remarkable difference was found between the summary SMRs and the summary rSMRs. The summary SMR for all cancers was 0.70 (95% CI, 0.63 to 0.79) whereas the summary rSMR was 1.38 (95% CI, 1.20 to 1.59). The summary SMR for leukemia was 0.88 (95% CI, 0.72 to 1.07), and the summary rSMR was 1.88 (95% CI, 1.20 to 2.95).

CONCLUSIONS

Our results suggest that adjustment for the healthy worker effect (i.e., rSMR) may be useful in meta-analyses of cohort studies reporting SMRs.

Possibility of Benzene Exposure in Workers of a Semiconductor Industry Based on the Patent Resources, 1990-2010

BACKGROUND

This study aimed to assess the possibility of benzene exposure in workers of a Korean semiconductor manufacturing company by reviewing the issued patents.

METHODS

A systematic patent search was conducted with the Google "Advanced Patent Search" engine using the keywords "semiconductor" and "benzene" combined with all of the words accessed on January 24, 2016.

RESULTS

As a result of the search, we reviewed 75 patent documents filed by a Korean semiconductor manufacturing company from 1994 to 2010. From 22 patents, we found that benzene could have been used as one of the carbon sources in chemical vapor deposition for capacitor; as diamond-like carbon for solar cell, graphene formation, or etching for transition metal thin film; and as a solvent for dielectric film, silicon oxide layer, nanomaterials, photoresist, rise for immersion lithography, electrophotography, and quantum dot ink.

CONCLUSION

Considering the date of patent filing, it is possible that workers in the chemical vapor deposition, immersion lithography, and graphene formation processes could be exposed to benzene from 1996 to 2010.

Chemical Use and Associated Health Concerns in the Semiconductor Manufacturing Industry

Background

Research on the status of many chemicals used in the semiconductor industry is needed. The purpose of this study was to describe the overall status of chemical use in the semiconductor industry in Korea and to examine it from a health perspective.

Methods

Data on the status of chemical use and safety data sheets at 11 of 12 major semiconductor workplaces in Korea were collected. The number of chemical products and chemical constituents, quantities of chemicals, and trade secret ingredients used, as well as the health hazards were examined.

Results

On average, 210 chemical products and 135 chemical constituents were used at the surveyed workplaces. Among all chemical products, 33% (range: 16-56%) contained at least one trade secret ingredient. Most of the trade secret ingredients were used in the photolithography process. Several carcinogens, including sulfuric acid, chromic acid, ethylene oxide, crystalline silica, potassium dichromate, and formaldehyde were also used. Only 29% (39 of 135) of the chemical constituents had occupational exposure limits, and more than 60% had no National Fire Protection Association health, safety, and reactivity ratings. Based on the aforementioned results, this study revealed the following. First, many chemical products and constituents are being used in the semiconductor industry and many products contained trade secret ingredients. Second, many products contained significant amounts of carcinogenic, mutagenic, and reproductive toxicant materials.

Conclusion

We conclude that protecting workers in the semiconductor industry against harm from chemical substances will be difficult, due to widespread use of trade secret ingredients and a lack of hazard information. The findings of the status of chemical use and the health and safety risks in semiconductor industry will contribute to epidemiological studies, safe workplace, and worker health protection.

Case-control study of brain and other central nervous system cancer among workers at semiconductor and storage device manufacturing facilities

OBJECTIVE

This study evaluated the relationship between brain and other central nervous system cancer ('CNS cancer') and exposures at two semiconductor and electronic module manufacturing facilities and at a storage device manufacturing facility.

METHODS

The case-control study, nested in a cohort of 126 836 employees, compared 120 CNS cancer cases and 1028 matched controls with respect to employment in 10 process groups and estimated cumulative exposure to 31 known or possible carcinogens.

RESULTS

CNS cancer was associated with module manufacturing operations at two facilities. Module manufacturing is a process that begins with production of ceramic substrates followed by attachment of completed semiconductor chips and metal-containing circuitry resulting in a high performing electronic device. Positive associations with the highest tertile of estimated cumulative exposure were found for several chemicals, including 2-butoxyethanol, cyclohexanone, ortho-dichlorobenzene, cadmium, molybdenum, trichloroethylene and vinyl chloride.

CONCLUSIONS

Results suggested positive associations between CNS cancer and specific operations and chemicals experienced in the semiconductor and electronic module manufacturing industry. However, lack of external support for these findings precludes a causal interpretation, and the observed associations may have been due to chance.

Occupational Characteristics of Semiconductor Workers with Cancer and Rare Diseases Registered with a Workers' Compensation Program in Korea

Background

The aim of this study was to describe the types of diseases that developed in semiconductor workers who have registered with the Korea Workers' Compensation and Welfare Service (KWCWS) and to identify potential common occupational characteristics by the type of claimed disease.

Methods

A total of 55 semiconductor workers with cancer or rare diseases who claimed to the KWCWS were compared based on their work characteristics and types of claimed diseases. Leukemia, non-Hodgkin lymphoma, and aplastic anemia were grouped into lymphohematopoietic (LHP) disorder.

Results

Leukemia (n = 14) and breast cancer (n = 10) were the most common complaints, followed by brain cancer (n = 6), aplastic anemia (n = 6), and non-Hodgkin lymphoma (n = 4). LHP disorders (n = 24) accounted for 43%. Sixty percent (n = 33) of registered workers (n = 55) were found to have been employed before 2000. Seventy-six percent (n = 42) of registered workers and 79% (n = 19) among the registered workers with LHP (n = 24) were found to be diagnosed at a relatively young age, ≤40 years. A total of 18 workers among the registered semiconductor workers were finally determined to deserve compensation for occupational disease by either the KWCWS (n = 10) or the administrative court (n = 8). Eleven fabrication workers who were compensated responded as having handled wafers smaller than eight inches in size. Eight among the 18 workers compensated (44 %) were found to have ever worked at etching operations.

Conclusion

The distribution of cancer and rare diseases among registered semiconductor workers was closely related to the manufacturing era before 2005, ≤8 inches of wafer size handled, exposure to clean rooms of fabrication and chip assembly operations, and etching operations.

Review for Retrospective Exposure Assessment Methods Used in Epidemiologic Cancer Risk Studies of Semiconductor Workers: Limitations and Recommendations

This article aims to provide a systematic review of the exposure assessment methods used to assign wafer fabrication (fab) workers in epidemiologic cohort studies of mortality from all causes and various cancers. Epidemiologic and exposure–assessment studies of silicon wafer fab operations in the semiconductor industry were collected through an extensive literature review of articles reported until 2017. The studies found various outcomes possibly linked to fab operations, but a clear association with the chemicals in the process was not found, possibly because of exposure assessment methodology. No study used a tiered assessment approach to identify similar exposure groups that incorporated manufacturing era, facility, fab environment, operation, job and level of exposure to individual hazardous agents. Further epidemiologic studies of fab workers are warranted with more refined exposure assessment methods incorporating both operation and job title and hazardous agents to examine the associations with cancer risk or mortality.

Comprehensive Evaluation of Hazardous Chemical Exposure Control System at a Semiconductor Manufacturing Company in South Korea

The goal of this study was to evaluate the hazardous chemical exposure control system in a semiconductor manufacturing company and recommend an appropriate exposure surveillance system for hazardous agents. We reviewed compliance-based chemical exposure data compiled between 2012 and 2014 by the study company. The chemical management system, characteristics of chemical use and hazardous gas monitoring system were also investigated. We evaluated the airborne isopropyl alcohol (IPA) and acetone generally used as cleaning solvents, volatile organic compounds and metals levels using internationally recommended sampling and analytical methods. Based on the results of past working environment measurement data and of our investigation, the overall current exposure to chemicals by semiconductor workers during routine production work appears to be controlled below occupational exposure limits. About 40% of chemical products used were found to contain at least one unidentifiable trade-secret substance. There are several situations and maintenance tasks that need special attention to reduce exposure to carcinogens as much as possible. In addition, a job-exposure matrix as a tool of surveillance system that can examine the exposure and health status of semiconductor workers according to type of operation and type of job or task is recommended.

Potential risk factors for haematological cancers in semiconductor workers

BACKGROUND

There has recently been increased interest in cancer incidence in electronics workers.

AIMS

To determine the cancer incidence ratio in electronics workers and the potential factors affecting the risk for development of cancer.

METHODS

Epidemiological study performed in electronics workers who were employed between 1999 and 2008 in South Korea. Cancer incidence ratio was analysed with respect to departments, divisions, job titles, gender, age, hepatitis B and C virus infection and work duration. We compared the incidence of haematological cancer in this cohort with that expected in the general population.

RESULTS

The study population was 56283. Overall, the standardized incidence ratio (SIR) for haematological cancer was 0.85. In particular, the SIR for leukaemia was 0.86 and for non-Hodgkin lymphoma (NHL) was 0.93, which were not statistically significant. The SIR for NHL was significantly increased [SIR 5.23, 95% confidence interval (CI) 1.31-20.95] in female office workers. We also found that the SIR for NHL was significantly increased in female workers who tested positive for hepatitis virus infection (SIR 7.69, 95% CI 1.08-54.60).

CONCLUSIONS

The raised SIR for NHL among female workers was due to potential risk factors such as hepatitis virus infection although additional research and an ongoing, long-term, prospective epidemiological cohort study is needed.

Exposure Reconstruction and Risk Analysis for Six Semiconductor Workers With Lymphohematopoietic Cancers

OBJECTIVE

To investigate whether workplace exposures to recognized lymphohematopoietic carcinogens were possibly related to cancers in six semiconductor-manufacturing workers.

METHODS

A job-exposure matrix was developed for chemical and physical process agents and anticipated by-products. Potential cumulative occupational exposures of the six cases were reconstructed. The role of workplace exposures in cancer was evaluated through quantitative risk assessment and by comparison with epidemiological literature.

RESULTS

Two workers were potentially exposed to agents capable of causing their diagnosed cancers. Reconstructed exposures were similar to levels in outdoor environments and lower than exposures associated with increased risks in epidemiological studies. Cancer risks were estimated to be less than 1 in 10,000 persons.

CONCLUSIONS

The development of cancer among the six workers was unlikely to be explained by occupational exposures to recognized lymphohematopoietic carcinogens.

Identifying the hazard characteristics of powder byproducts generated from semiconductor fabrication processes

Semiconductor manufacturing processes generate powder particles as byproducts which potentially could affect workers' health. The chemical composition, size, shape, and crystal structure of these powder particles were investigated by scanning electron microscopy equipped with an energy dispersive spectrometer, Fourier transform infrared spectrometry, and X-ray diffractometry. The powders generated in diffusion and chemical mechanical polishing processes were amorphous silica. The particles in the chemical vapor deposition (CVD) and etch processes were TiO(2) and Al(2)O(3), and Al(2)O(3) particles, respectively. As for metallization, WO(3), TiO(2), and Al(2)O(3) particles were generated from equipment used for tungsten and barrier metal (TiN) operations. In photolithography, the size and shape of the powder particles showed 1-10 μm and were of spherical shape. In addition, the powders generated from high-current and medium-current processes for ion implantation included arsenic (As), whereas the high-energy process did not include As. For all samples collected using a personal air sampler during preventive maintenance of process equipment, the mass concentrations of total airborne particles were < 1 μg, which is the detection limit of the microbalance. In addition, the mean mass concentrations of airborne PM10 (particles less than 10 μm in diameter) using direct-reading aerosol monitor by area sampling were between 0.00 and 0.02 μg/m(3). Although the exposure concentration of airborne particles during preventive maintenance is extremely low, it is necessary to make continuous improvements to the process and work environment, because the influence of chronic low-level exposure cannot be excluded.

The health impacts of semiconductor production: an epidemiologic review

BACKGROUND

Despite concerns over the harmful health effects of semiconductor production, epidemiological studies have shown mixed results.

OBJECTIVES

We aim to critically appraise epidemiologic studies to date, and to suggest future research and actions to protect workers in semiconductor industry.

METHODS

Epidemiologic studies were identified through electronic database searches, review of reference lists of relevant published works, and expert consultations, and were narratively reviewed.

RESULTS

Most evidence suggests reproductive risks from fabrication jobs, including spontaneous abortion (SAB), congenital malformation, and reduced fertility. Although chemicals have been suspected as causal agents, knowledge of the likely contribution(s) from specific exposures is still limited. Evidence of cancer risk seems to be equivocal. However, the available studies had serious limitations including healthy worker effects (HWEs), information bias, and insufficient power, all of which are associated with underestimation. Nevertheless, excess risks for non-Hodgkin's lymphoma (NHL), leukemia, brain tumor, and breast cancer were observed.

CONCLUSIONS

Monitoring and innovative research based on international collaboration with a focus on sentinel events are required.

Leukemia and non-Hodgkin lymphoma in semiconductor industry workers in Korea

Reports of leukemia and non-Hodgkin lymphoma (NHL), cancers known to have a similar pathophysiology, among workers in the semiconductor industry have generated much public concern in Korea. This paper describes cases reported to the NGO Supporters for the Health and Rights of People in the Semiconductor Industry (SHARPs). We identified demographic characteristics, occupational, and disease history, for 17 leukemia and NHL cases from the Giheung Samsung semiconductor plant, diagnosed from November 2007 to January 2011. Patients were relatively young (mean = 28·5 years, SD = 6·5) at the time of diagnosis and the mean latency period was 104·3 months (SD = 65·8). Majority of the cases were fabrication operators (11 workers among 17) and 12 were hired before 2000. Six cases worked in the etching or diffusion process. The evidence to confirm the causal relationship between exposures in the semiconductor industry and leukemia or NHL remains insufficient and a more formal, independent study of the exposure-disease relationship in this occupation is needed. However, workers should be protected from the potential exposures immediately.

Cancer mortality and incidence in korean semiconductor workers

Objectives

The purpose of this study was to evaluate cancer risks in the Korean semiconductor industry.

Methods

A retrospective cohort study was performed in eight semiconductor factories between 1998 and 2008. The number of subjects was 113,443 for mortality and 108,443 for incidence. Standardized mortality ratios (SMR) and standardized incidence ratios (SIR) were calculated.

Results

The SMR of leukemia was 0.39 (95% Confidence Interval 0.08-1.14) in males (2 cases) and 1.37 (0.55-2.81) in females (7 cases). The SMR of non-Hodgkin's lymphoma (NHL) was 1.33 (0.43-3.09, 5 cases) in males and 2.5 (0.68-6.40, 4 cases) in females. The SIR of leukemia was 0.69 (0.30-1.37, 8 cases) in males and 1.28 (0.61-2.36, 10 cases) in females. The SIR of NHL in females was 2.31 (1.23-3.95, 13 cases) and that of thyroid cancer in males was 2.11 (1.49-2.89, 38 cases). The excess incidence of NHL was significant in female assembly operators [SIR=3.15 (1.02-7.36, 5 cases)], but not significant in fabrication workers. The SIR of NHL in the group working for 1-5 years was higher than the SIR of NHL for those working for more than five years. The excess incidence of male thyroid cancer was observed in both office and manufacturing workers.

Conclusion

There was no significant increase of leukemia in the Korean semiconductor industry. However, the incidence of NHL in females and thyroid cancer in males were significantly increased even though there was no definite association between work and those diseases in subgroup analysis according to work duration. This result should be interpreted cautiously, because the majority of the cohort was young and the number of cases was small.