Sangjun Choi

A Comprehensive Review of Arsenic Levels in the Semiconductor Manufacturing Industry

This paper presents a summary of arsenic level statistics from air and wipe samples taken from studies conducted in fabrication operations. The main objectives of this study were not only to describe arsenic measurement data but also, through a literature review, to categorize fabrication workers in accordance with observed arsenic levels. All airborne arsenic measurements reported were included in the summary statistics for analysis of the measurement data. The arithmetic mean was estimated assuming a lognormal distribution from the geometric mean and the geometric standard deviation or the range. In addition, weighted arithmetic means (WAMs) were calculated based on the number of measurements reported for each mean. Analysis of variance (ANOVA) was employed to compare arsenic levels classified according to several categories such as the year, sampling type, location sampled, operation type, and cleaning technique. Nine papers were found reporting airborne arsenic measurement data from maintenance workers or maintenance areas in semiconductor chip-making plants. A total of 40 statistical summaries from seven articles were identified that represented a total of 423 airborne arsenic measurements. Arsenic exposure levels taken during normal operating activities in implantation operations (WAM = 1.6 μg m⁻³, no. of samples = 77, no. of statistical summaries = 2) were found to be lower than exposure levels of engineers who were involved in maintenance works (7.7 μg m⁻³, no. of samples = 181, no. of statistical summaries = 19). The highest level (WAM = 218.6 μg m⁻³) was associated with various maintenance works performed inside an ion implantation chamber. ANOVA revealed no significant differences in the WAM arsenic levels among the categorizations based on operation and sampling characteristics. Arsenic levels (56.4 μg m⁻³) recorded during maintenance works performed in dry conditions were found to be much higher than those from maintenance works in wet conditions (0.6 μg m⁻³). Arsenic levels from wipe samples in process areas after maintenance activities ranged from non-detectable to 146 μg cm⁻², indicating the potential for dispersion into the air and hence inhalation. We conclude that workers who are regularly or occasionally involved in maintenance work have higher potential for occupational exposure than other employees who are in charge of routine production work. In addition, fabrication workers can be classified into two groups based on the reviewed arsenic exposure levels: operators with potential for low levels of exposure and maintenance engineers with high levels of exposure. These classifications could be used as a basis for a qualitative ordinal ranking of exposure in an epidemiological study.

Trends in Occupational Asbestos Exposure and Asbestos Consumption over Recent Decades in Korea

Abstract In Korea, national statistics for asbestos exposure levels covering various asbestos industries and associated with specific years have never been published. The authors analyzed 2,089 asbestos exposure data sets compiled from 1995 through 2006. Exposure levels were characterized according to type of asbestos industry and year. Asbestos exposure levels have decreased over time, dropping sharply from 0.92 fibers/cc (f/cc) in 1996 to 0.60 f/cc in 1997, to 0.19 f/cc in 1998, and to 0.06 f/cc in 1999, possibly in part because of enforcement of 1997 legislation banning the use of amosite and crocidolite. In particular, a substantial reduction in asbestos exposure levels was most evident among primary industries handling raw asbestos directly. Asimilar relationship wasfound between a significant decline in asbestos consumption volume and the timing of regulation enforcement.

Developing Asbestos Job Exposure Matrix Using Occupation and Industry Specific Exposure Data (1984–2008) in Republic of Korea

Background The goal of this study is to develop a general population job-exposure matrix (GPJEM) on asbestos to estimate occupational asbestos exposure levels in the Republic of Korea. Methods Three Korean domestic quantitative exposure datasets collected from 1984 to 2008 were used to build the GPJEM. Exposure groups in collected data were reclassified based on the current Korean Standard Industrial Classification (9th edition) and the Korean Standard Classification of Occupations code (6th edition) that is in accordance to international standards. All of the exposure levels were expressed by weighted arithmetic mean (WAM) and minimum and maximum concentrations. Results Based on the established GPJEM, the 112 exposure groups could be reclassified into 86 industries and 74 occupations. In the 1980s, the highest exposure levels were estimated in “knitting and weaving machine operators” with a WAM concentration of 7.48 fibers/mL (f/mL); in the 1990s, “plastic products production machine operators” with 5.12 f/mL, and in the 2000s “detergents production machine operators” handling talc containing asbestos with 2.45 f/mL. Of the 112 exposure groups, 44 groups had higher WAM concentrations than the Korean occupational exposure limit of 0.1 f/mL. Conclusion The newly constructed GPJEM which is generated from actual domestic quantitative exposure data could be useful in evaluating historical exposure levels to asbestos and could contribute to improved prediction of asbestos-related diseases among Koreans.

Estimating Benzene Exposure Level over Time and by Industry Type through a Review of Literature on Korea

The major purpose of this study is to construct a retrospective exposure assessment for benzene through a review of literature on Korea. Airborne benzene measurements reported in 34 articles were reviewed. A total of 15,729 individual measurements were compiled. Weighted arithmetic means [AM(w)] and their variance calculated across studies were summarized according to 5-year period intervals (prior to the 1970s through the 2010s) and industry type. Industries were classified according to Korea Standard Industrial Classification (KSIC) using information provided in the literature. We estimated quantitative retrospective exposure to benzene for each cell in the matrix through a combination of time and KSIC. Analysis of the AM(w) indicated reductions in exposure levels over time, regardless of industry, with mean levels prior to the 1980–1984 period of 50.4 ppm (n = 2,289), which dropped to 2.8 ppm (n = 305) in the 1990–1994 period, and to 0.1 ppm (n = 294) in the 1995–1999 period. There has been no improvement since the 2000s, when the AM(w) of 4.3 ppm (n = 6,211) for the 2005–2009 period and 4.5 ppm (n = 3,358) for the 2010–2013 period were estimated. A comparison by industry found no consistent patterns in the measurement results. Our estimated benzene measurements can be used to determine not only the possibility of retrospective exposure to benzene, but also to estimate the level of quantitative or semiquantitative retrospective exposure to benzene.

Extremely Low Frequency-Magnetic Field (ELF-MF) Exposure Characteristics among Semiconductor Workers

We assessed the exposure of semiconductor workers to extremely low frequency-magnetic fields (ELF-MF) and identified job characteristics affecting ELF-MF exposure. These were demonstrated by assessing the exposure of 117 workers involved in wafer fabrication (fab) and chip packaging wearing personal dosimeters for a full shift. A portable device was used to monitor ELF-MF in high temporal resolution. All measurements were categorized by operation, job and working activity during working time. ELF-MF exposure of workers were classified based on the quartiles of ELF-MF distribution. The average levels of ELF-MF exposure were 0.56 µT for fab workers, 0.59 µT for chip packaging workers and 0.89 µT for electrical engineers, respectively. Exposure to ELF-MF differed among types of factory, operation, job and activity. Workers engaged in the diffusion and chip testing activities showed the highest ELF-MF exposure. The ELF-MF exposures of process operators were found to be higher than those of maintenance engineers, although peak exposure and/or patterns varied. The groups with the highest quartile ELF-MF exposure level are operators in diffusion, ion implantation, module and testing operations, and maintenance engineers in diffusion, module and testing operations. In conclusion, ELF-MF exposure among workers can be substantially affected by the type of operation and job, and the activity or location.

Estimates of the Number of Workers Exposed to Diesel Engine Exhaust in South Korea from 1993 to 2013

Background The aim of this study was to estimate the number of workers exposed to diesel engine exhaust (DEE) by industry and year in the Republic of Korea. Method The estimates of workers potentially exposed to DEE in the Republic of Korea were calculated by industry on the basis of the carcinogen exposure (CAREX) surveillance system. The data on the labor force employed in DEE exposure industries were obtained from the Census on Establishments conducted by the Korea National Statistical Office from 1993 to 2013. The mean values of prevalence rates adopted by EU15 countries were used as the primary exposure prevalence rates. We also investigated the exposure prevalence rates and exposure characteristics of DEE in 359 workplaces representing 11 industries. Results The total number of workers exposed to DEE were estimated as 270,014 in 1993 and 417,034 in 2013 (2.2% of the total labor force). As of 2013, the industry categorized as “Land transport” showed the highest number of workers exposed to DEE with 174,359, followed by “Personal and household services” with 70,298, “Construction” with 45,555, “Wholesale and retail trade and restaurants and hotels” with 44,005, and “Sanitation and similar services” with 12,584. These five industries, with more than 10,000 workers exposed to DEE, accounted for 83% of the total DEE-exposed workers. Comparing primary prevalence rates used for preliminary estimation among 49 industries, “Metal ore mining” had the highest rate at 52.6%, followed by “Other mining” with 50.0%, and “Land transport” with 23.6%. Conclusion The DEE prevalence rates we surveyed (1.3–19.8%) were higher than the primary prevalence rates. The most common emission sources of DEE were diesel engine vehicles such as forklifts, trucks, and vans. Our estimated numbers of workers exposed to DEE can be used to identify industries with workers requiring protection from potential exposure to DEE in the Republic of Korea.

Job-specific Questionnaire for Estimating Exposure to Hazardous Agents among Semiconductor Workers

ABSTRACT Objectives: One major limitation encountered in retrospective exposure assessment for epidemiological study is the lack of exposure records and information maintained by companies which if they existed would allow the estimation of past exposure to hazardous operations and agents. This study developed a job-specific questionnaire(JSQ) to estimate exposure profiles among semiconductor workers, including operation and job. Methods: This JSQ can be directly applied to workers who work or have worked in a wafer fabrication or a chip packaging and assembly facility. Results and Conclusions: We used this JSQ to obtain past exposure information from semiconductor workers via face-to-face investigation. Major contents include questions on the facilities, operations and jobs to which they have been exposed since they *Corresponding author: Dong Uk Park, Tel: 02-3668-4707, E-mail: pdw545@gmail.comDepartment of Environmental Health, Korea National Open University, 169 Dongsung-dong, Jongroku, Seoul, KoreaReceived: February 3, 2016, Revised: March 4, 2016, Accepted: March 14, 2016This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License(http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

1132 Estimation of lead exposure prevalence in korean population through combining multiple experts’ judgment based on objective data sources

Objectives Estimation of exposure prevalences of carcinogens is important for preventing occupational cancers. For developing Korean CAREX (CARcinogen EXposure) which is a carcinogen surveillance system employed in many countries, as an exemplary carcinogen, we estimated lead exposure prevalences in Korean working population. Methods We used three nationwide data sources to retrieve objective default estimates of lead exposure prevalence across industries: the work-environment monitoring database (WEMD), the special health examination database (SHED), and the Work Environment Condition Survey (WECS). Furthermore, we surveyed experts for their judgment about lead exposure prevalence across industries after reviewing the default estimates computed from aforementioned three exposure databases. We developed various estimation methods combining experts’ judgment, and then compared with each other. The 2010 Census was used as the reference population to estimate the number of lead-exposed workers for the 228 industries through multiplying the exposure prevalence with the number of workers in each industry. Results Default estimates of exposure prevalence for 228 industries were calculated using the WEMD and SHED collected between 2009–2011, and the 2009 WECS. A total of 52 experts who have 20 or more experience in industrial hygiene practice participated in the study and provided their judgment on the lead exposure prevalences as a number for the 228 industries. Among various estimation methods, the median values of experts’ responses were selected for our estimates of lead exposure prevalence in each industry. As a result, a total of 129,247 Korean workers was estimated to be exposed to lead in the year of 2010. Conclusions We developed a method estimating exposure prevalences combining experts’ judgment based on objective databases. Our effort for estimating the exposure prevalences of CAREX may introduce an unbiased approach to the development process accounting for uncertainty of exposure.

1131 Combining lead exposure measurements and experts’ opinion through a bayesian framework

Objectives CAREX (CARcinogen EXposure) is a carcinogen surveillance system employed in many countries. To initiate Korean CAREX, we focused on estimating the exposure intensity of lead across industries, which is a suspected carcinogen. Methods We extracted airborne lead measurements from the work environment measurement database (WEMD) which is the Korean nationwide measurement database. In addition, we elicited the experts’ opinion about lead exposure intensity across industries by conducting a questionnaire. Experts provided estimates of lead exposure levels as the boundary of the 5th and 95th percentiles. We assumed that experts provided their estimates based on the assumption of log-normal distributions of exposure. First, for each industry, estimates of log-transformed geometric means (logGM) and log-transformed geometric standard deviations (logGSD) were extracted from the experts’ responses, followed by combining them to quantify the experts’ prior Normal-Inverse-Gamma prior distribution. Then, the corresponding logGM and logGSD from lead measurement data for each industry were updated with the experts’ prior distribution through a Bayesian framework, yielding posterior distributions of logGM and logGSD. Results WEMD contains 83 035 airborne lead measurements collected between 2002–2007. Total 17 occupational hygiene professionals with more than 20 year experience provided lead exposure estimates. In industries where measurement data is abundant, the measurement data dominate the posterior exposure estimates, while in industries with a limited number of measurements, experts’ opinion played an important role in determining posterior exposure estimates. For example, rubber manufacturing industry with 246 measurements (GM 1.72; GSD 1.94) and 6 experts’ responses (GM 0.79; GSD 6.73) showed posterior exposure estimates of GM 1.60 and GSD 2.34. Conclusions Our method of estimating the exposure intensity of CAREX may introduce an unbiased approach to the development process by utilising both prior knowledge of experts and measurement data simultaneously. In addition, it will supply a framework for future updates.

Chemical use in the semiconductor manufacturing industry

ABSTRACT Background: The semiconductor industry is known to use a number of chemicals, but little is known about the exact chemicals used due to the ingredients being kept as a trade secret. Objectives: The objective of this study was to analyze chemical use using a safety data sheet (SDS) and chemical inventory provided by a major semiconductor company, which operated two factories (A and B). Methods: Descriptive statistics were obtained on the number of chemical products and ingredients, photoresists, and carcinogens, classified by the International Agency for Research on Cancer (IARC), as well as trade secret ingredients. The total chemical use per year was estimated from chemical inventories mass (kg). Results: A total of 428 and 432 chemical products were used in factories A and B, respectively. The number of pure chemical ingredients, after removing both trade secret ingredients and multiple counting, was 189 and 157 in factories A and B, respectively. The number of products containing carcinogens, such as sulfuric acid, catechol, and naphthalene was 47/428 (A) and 28/432 (B). Chemicals used in photolithography were 21% (A) and 26% (B) of all chemical products, and more than 97% among them were chemicals containing trade secret ingredients. Conclusions: Each year, 4.3 and 8.3 tons of chemicals were used per person in factories A and B, respectively. Because of the high level of commercial secrecy and the use of many unregulated chemicals, more sustainable policies and methods should be implemented to address health and safety issues in the semiconductor industry.