Frank J. Hearl

Long-Term Exposure to Silica Dust and Risk of Total and Cause-Specific Mortality in Chinese Workers: A Cohort Study

A retro-prospective cohort study by Weihong Chen and colleagues provides new estimates for the risk of total and cause-specific mortality due to long-term silica dust exposure among Chinese workers.

Estimating historical respirable crystalline silica exposures for Chinese pottery workers and iron/copper, tin, and tungsten miners

Collaborative studies of Chinese workers, using over four decades of dust monitoring data, are being conducted by the National Institute for Occupational Safety and Health (NIOSH) and Tongji Medical University in China. The goal of these projects is to establish exposure-response relationships for the development of diseases such as silicosis or lung cancer in cohorts of pottery and mine workers. It is necessary to convert Chinese dust measurements to respirable silica measurements in order to make results from the Chinese data comparable to other results in the literature. This article describes the development of conversion factors and estimates of historical respirable crystalline silica exposure for Chinese workers. Ambient total dust concentrations (n>17000) and crystalline silica concentrations (n=347) in bulk dust were first gathered from historical industrial hygiene records. Analysis of the silica content in historical bulk samples revealed no trend from 1950 up to the present. During 1988-1989, side-by-side airborne dust samples (n=143 pairs) were collected using nylon cyclones and traditional Chinese samplers in 20 metal mines and nine pottery factories in China. These data were used to establish conversion factors between respirable crystalline silica concentrations and Chinese total dust concentrations. Based on the analysis of the available evidence, conversion factors derived from the 1988-1989 sampling campaign are assumed to apply to other time periods in this paper. The conversion factors were estimated to be 0.0143 for iron/copper, 0.0355 for pottery factories, 0.0429 for tin mines, and 0.0861 for tungsten mines. Conversion factors for individual facilities within each industry were also calculated. Analysis of variance revealed that mean conversion factors are significantly different among facilities within the iron/copper industry and within the pottery industry. The relative merits of using facility-specific conversion factors, industry-wide conversion factors, or a weighted average of the two are discussed. The exposure matrix of the historical Chinese total dust concentrations was multiplied by these conversion factors to obtain an exposure matrix of historical respirable crystalline silica concentrations.

Aggregate Exposure and Cumulative Risk Assessment—Integrating Occupational and Non-occupational Risk Factors

Occupational exposure limits have traditionally focused on preventing morbidity and mortality arising from inhalation exposures to individual chemical stressors in the workplace. While central to occupational risk assessment, occupational exposure limits have limited application as a refined disease prevention tool because they do not account for all of the complexities of the work and non-occupational environments and are based on varying health endpoints. To be of greater utility, occupational exposure limits and other risk management tools could integrate broader consideration of risks from multiple exposure pathways and routes (aggregate risk) as well as the combined risk from exposure to both chemical and non-chemical stressors, within and beyond the workplace, including the possibility that such exposures may cause interactions or modify the toxic effects observed (cumulative risk). Although still at a rudimentary stage in many cases, a variety of methods and tools have been developed or are being used in allied risk assessment fields to incorporate such considerations in the risk assessment process. These approaches, which are collectively referred to as cumulative risk assessment, have potential to be adapted or modified for occupational scenarios and provide a tangible path forward for occupational risk assessment. Accounting for complex exposures in the workplace and the broader risks faced by the individual also requires a more complete consideration of the composite effects of occupational and non-occupational risk factors to fully assess and manage worker health problems. Barriers to integrating these different factors remain, but new and ongoing community-based and worker health-related initiatives may provide mechanisms for identifying and integrating risk from aggregate exposures and cumulative risks from all relevant sources, be they occupational or non-occupational.

Working safely with robot workers: Recommendations for the new workplace

ABSTRACT The increasing use of robots in performing tasks alongside or together with human co-workers raises novel occupational safety and health issues. The new 21st century workplace will be one in which occupational robotics plays an increasing role. This article describes the increasing complexity of robots and proposes a number of recommendations for the practice of safe occupational robotics.

Quartz Analyses of the Bulk Dust Samples Collected by the National Occupational Health Survey of Mining

The National Institute for Occupational Safety and Health (NIOSH) conducted the National Occupational Health Survey of Mining (NOHSM) over a 6-year period, which began in May 1984 and ended in Augu...

Current Exposure Guidelines for Particulates Not Otherwise Classified or Regulated: History and Rationale

Abstract Exposure limits and guidelines for particles not otherwise classified or regulated (PNOC/R) evolved from several important studies of pneumoconiosis performed early in the 20th century. These studies indicated that exposure to dust concentrations of less than 50 million particles per cubic foot (mppcf) and with low crystalline silica concentrations did not appear to lead to the development of disabling lung disease. Consequently, dusts containing less than 5 percent crystalline silica were termed “nuisance dusts,” and an exposure limit of 50 mppcf was recommended. With the advent of mass sampling technology and the ability to sample directly for respirable dust, exposure limits migrated to total and respirable nuisance dust exposure limits of 15 and 5 mg/m3, respectively, for dusts containing less than 1 percent crystalline silica. Regulatory exposure limits were established by incorporating these exposure guidelines that were in existence when the enabling legislation was enacted. Changes to reg...

National Occupational Health Survey of Mining Query System

Abstract The National Institute for Occupational Safety and Health (NIOSH) conducted a project called the National Occupational Health Survey of Mining (NOHSM) from 1984 to 1989. The NOHSM consisted of 491 mine surveys. The mines were selected so as to be statistically representative of the entire U.S. mining industry. At each mine, NIOSH employees obtained data regarding occupational hygiene programs, potential exposure to chemical and physical agents, and bulk dust samples. The NOHSM survey data have been automated in the NOHSM Query System. This system allows queries to be processed against the data collected during the NOHSM survey. The NOHSM Query System was developed to be user friendly so that end-users can process their own queries against the NOHSM data. This was accomplished by making the system key driven with on-line help, and simplifying the query formulation process by minimizing the selections. There are two steps in formulating a query. Step one is deciding which data to retrieve or how to...