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Occupational Lead Surveillance -- Taiwan, July-December 1993

Lead poisoning has been recognized as an occupational disease for centuries and has been linked with both severe and subtle health damage (1-3). In July 1993, the government of Taiwan initiated a compulsory system * for surveillance of elevated blood lead levels (BLLs) among workers in that country (4). All lead-exposed workers in lead-using factories ** are identified and included in the lead surveillance system. This report summarizes findings from this program for July-December 1993.

A total of 18 categories of production processes (e.g., battery recycling or manufacturing, lead smelting, plastic stabilizer additive processing, and lead-based paint production) or occupation/job categories constitute the high-lead exposure group. Lead-exposed workers in these settings are required to have their BLLs monitored annually by one of 22 specified, certified hospital laboratories. Based on job titles and an occupation register published by the Labor Council of Taiwan, a minimum of 4500 workers in Taiwan were directly exposed to lead-contaminated work environments (at exposure levels ranging from 0.002 mg/m3 to 3.051 mg/m3 ***), and 10-fold more workers were indirectly exposed (e.g., secretaries who work at the same factories but in jobs that do not entail direct lead exposure).

Employers are required by law to report at least annually to local health bureaus and labor inspection offices the BLLs and results of health examinations (specifically designed for lead-exposed workers and performed at one of the specified hospitals). Labor Council factory inspectors are responsible for enforcing this law. To ensure employer and worker participation, employers are subject to fines equivalent to $1200-$2400 U.S. for delayed reporting (i.e., beyond 3 months) or failure to report. To encourage continued reporting by local health officials, the Ministry of Health publishes a quarterly report that contains county-specific BLL results and complete rates of follow-up.

During July-December 1993, BLLs were tested in 2905 lead-exposed workers. The mean BLL in males (n=1941) was 15.0 ug/dL (standard deviation {sd}= plus or minus 15.1 ug/dL) and in females (n=964), 12.5 ug/dL (sd= plus or minus 12.2 ug/dL). Mean BLLs were significantly (p less than 0.05, Z test) higher than BLLs for the total population aged greater than or equal to 15 years in Taiwan (9.6 ug/dL for males; 7.4 ug/dL for females) (5). In addition, BLLs in 287 (9.9%) workers exceeded the applicable regulatory level (40 ug/dL for males; 30 ug/dL for females).

Most monitored workers were employed in soldering/cable stripping (452) and in battery recycling/manufacturing (364) Table_1. Mean BLLs were highest among battery workers (34.6 ug/dL) and plastic manufacturers (27.5 ug/dL), and BLLs were elevated for approximately 25% of workers in plastic-manufacturing factories and 50% in battery-producing factories. Mean BLLs and proportions of workers with elevated BLLs were lowest in the following exposure categories: electric plating and painting, railroad workers, traffic police, and soldering/cable stripping.

The surveillance system in Taiwan also provides for an intervention team (including epidemiologists, industrial hygienists, and physicians) to evaluate the workplaces of workers with elevated BLLs. This response includes monitoring ambient lead exposure levels, evaluating the company's health and safety procedures, providing technical assistance to reduce lead exposure, and improving high-risk work practices and worker behaviors (including prevention of inadvertent transport of lead from the workplace to the worker's home). Through February 1995, the intervention teams had investigated the workplaces of 201 (70%) of the 287 workers with elevated BLLs. Priorities for follow-up are based on the BLLs of the workers involved. Reported by: TN Wu, PhD, CY Shen, PhD, GY Yang, MD, SH Liou, MD, KN Ko, MPH, SL Chao, MPH, CC Hsu, MPH, JS Lai, PhD, PY Chang, MD, Disease Surveillance and Quarantine Svc, Ministry of Health, Taiwan, Republic of China. Div of Surveillance, Hazard Evaluations, and Field Studies, National Institute for Occupational Safety and Health, CDC.

Editorial Note

Editorial Note: The establishment of the compulsory occupational lead surveillance system described in this report is an important step in industrial hygiene and occupational disease prevention in Taiwan, and similar systems may be used in other countries and settings. In particular, the surveillance system in Taiwan indicates the usefulness of exposure information to target monitoring activities and using that information to target intervention efforts. This system should facilitate improvements in the industrial hygiene of the work environment, assist in evaluating the effects of intervention, and reduce both primary and secondary (e.g., take-home) exposures to lead.

Since the mid-1980s, occupational lead surveillance programs have been developed in both Taiwan and the United States. In both countries, these systems are laboratory-based and legally mandated; however, each system also has distinguishing features Table_2. In particular, in Taiwan, companies subject to surveillance are predetermined based on predicted potential for exposure and are required to report to the government. In comparison, in the United States, companies are required to self-identify the existence of lead exposures and then to comply with the requirements of the Occupational Safety and Health Administration (OSHA) General Industry (6) and/or Construction Standards (7), which include provisions for environmental and medical monitoring. In Taiwan, 70% of the workers in workplaces where elevated BLLs were detected received follow-up interventions. In the United States, follow-up interventions vary according to state resources and BLLs. Seven of the 14 CDC-funded state-based surveillance programs have formal or informal agreements with OSHA for referral and follow-up of cases. However, the apparent exclusion of the nonman-ufacturing sector (e.g., construction) is an important potential limitation in Taiwan and may preclude identification of new hazards or sources of lead poisoning, as well as reflect an underestimate of the magnitude of the problem outside of the manufacturing sector. Finally, the reported compliance with monitoring was relatively high in Taiwan (2950 {66%} workers monitored of an estimated 4500 exposed); in comparison, based on an assessment in California in 1986, the requirements of the OSHA standard for air and blood lead monitoring have been adhered to by only a small proportion of facilities **** (8). Despite this apparently low compliance with biologic monitoring provisions of the standard, state-based surveillance programs have succeeded in identifying industries and occupations where lead hazards remain (9).

Although the systems in Taiwan and the United States differ, the beneficial public health effects of surveillance in each country are substantial -- large numbers of workers with exposure and/or elevated BLLs have been identified (10), monitored, and trained to prevent future lead poisoning. The surveillance system in Taiwan reflects efforts to establish improved occupational health surveillance in conjunction with rapid growth in industrial capacity. The legal mandate in Taiwan enables the incorporation of surveillance requirements as integral parts of standard business operations, rather than only as reactive responses to a public health problem, and emphasizes that occupational health concerns are an important part of industrialization.

References

  1. La Dou J. Occupational medicine. Englewood Cliffs, New Jersey: Prentice Hall, 1990:297.

  2. Rempel D. The lead-exposed worker. JAMA 1989;262:532.

  3. Hamilton A. Exploring the dangerous trades. Boston: Little Brown, 1943.

  4. Wu TN, Shen CY, Yang GY, et al. Establishment of an occupational diseases surveillance system to monitor blood lead levels in Taiwan. Prev Med 1995 (in press).

  5. Liou SH, Wu TN, Chiang HC. A nation-wide survey of blood lead level in Taiwan. Taipei, Taiwan: Taiwan Department of Health, 1992.

  6. Office of the Federal Register. Code of federal regulations: occupational safety and health standards. Subpart Z: Toxic and hazardous substances -- lead. Washington, DC: Office of the Federal Register, National Archives and Records Administration, 1985. (29 CFR *** 1910.1025).

  7. Occupational Safety and Health Administration, US Department of Labor. Lead exposure in construction: interim final rule. Federal Register 1993;58:26590-649. (29 CFR *** 1926).

  8. Rudolph L, Sharp D, Samuels S, Perkins C, Rosenberg J. Environmental and biological monitoring for lead exposure in California workplaces. Am J Public Health 1990;80:921-5.

  9. Rabin R, Brooks D, Davis L. Elevated blood lead levels among construction workers in the Massachusetts Occupational Lead Registry. Am J Public Health 1994;84:1483-5.

  10. CDC. Adult blood lead epidemiology and surveillance -- United States, fourth quarter, 1993. MMWR 1994;43:246-7.

* Based on the Labor Safety and Health Law (enacted in 1974 by the Labor Council of Taiwan). 

** Defined according to the worker's occupation/job category and the company's production process, which is registered on the license of every factory in Taiwan. 

*** Data from a Labor Council survey of working environments of lead-related workers; in the United States, the maximum allowable exposure to lead in air is 50 ug/m3 (0.050 mg/m3). 

**** In 1986, an estimated 2.6% of facilities using lead had ever done any environmental monitoring, and 1.4% of facilities (employing 2.6% of potentially lead-exposed workers) had routine biologic monitoring programs.



Table_1
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TABLE 1. Blood lead levels (BLLs) among lead-exposed workers, by production
process/occupation -- Taiwan, July-December 1993
===================================================================================
                                   Workers examined             Elevated BLLs *
                        -------------------------------------- --------------------
                                        Mean
Production process/                      BLL                     No.
  Occupation            No.     (%)    (ug/dL)    (SD +)       Workers    (%)
-----------------------------------------------------------------------------------
Mine smelting and
  foundry workers       152   (  5.2)   13.1   (+/-14.2 ug/dL)    8     ( 5.3)
Electric plating
  and painting          134   (  4.6)    7.1   (+/- 3.1 ug/dL)    0
Metal working            93   (  3.2)   12.9   (+/-11.0 ug/dL)    3     ( 3.2)
Plastic manufacturing   154   (  5.3)   27.5   (+/-20.9 ug/dL)   45     (29.2)
Soldering/Cable
  stripping             452   ( 15.6)    8.6   (+/- 8.5 ug/dL)    6     ( 1.3)
Battery recycling/
  manufacturing         364   ( 12.5)   34.6   (+/-15.9 ug/dL)  176     (48.4)
Railroad workers         32   (  1.1)   15.6   (+/-10.7 ug/dL)    0
Traffic police          258   (  8.9)   13.1   (+/- 5.8 ug/dL)    1     ( 0.4)
Other/Undefined        1266   ( 43.6)    9.7   (+/- 9.7 ug/dL)   48     ( 3.8)

Total                  2905   (100.0)                           287     ( 9.9)
-----------------------------------------------------------------------------------
* BLL >=40 ug/dL for males; BLL >=30 ug/dL for females.
+ Standard deviation.
===================================================================================

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Table_2
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TABLE 2. Occupational blood lead level (BLL) surveillance systems, by selected
characteristics -- Taiwan and United States
================================================================================
Characteristic           Taiwan                      United States

Reporting                Compulsory                  Compulsory in 32 states *
Coverage                 Nationwide                  State-based
Target population        Lead-exposed workers        Adult population +
                           (cohort)                    (cross-sectional sample
Frequency of
  surveillance           12 Months                   Varies (depending on BLL)
Routine evaluation
  of compliance
  reporting              Yes                         Varies by state
Epidemiologic            Yes (for every              Yes (for every worker
  intervention             worker whose BLL            whose BLL exceeds
                           exceeds a specified         a specified level &)
                           level)
--------------------------------------------------------------------------------
* Alabama, Arizona, California, Colorado, Connecticut, Florida, Georgia,
  Illinois, Iowa, Maine, Maryland, Massachusetts, Michigan, Minnesota,
  Mississippi, Nebraska, New Hampshire, New Jersey, New Mexico, New York, North
  Carolina, Ohio, Oklahoma, Oregon, Pennsylvania, South Carolina, Texas, Utah,
  Vermont, Washington, Wisconsin, and Wyoming. The national adult surveillance
  system receives reports from 22 states.
+ Aged >=16 years.
& Follow-up approach varies by state. Medical removal of workers with elevated
  BLLs is mandated by the Occupational Safety and Health Administration in the
  General Industry and/or Construction Standards.
================================================================================

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