Occupational safety and health criteria for responsible development of nanotechnology.

Organizations around the world have called for the responsible development of nanotechnology. The goals of this approach are to emphasize the importance of considering and controlling the potential adverse impacts of nanotechnology in order to develop its capabilities and benefits. A primary area of concern is the potential adverse impact on workers, since they are the first people in society who are exposed to the potential hazards of nanotechnology. Occupational safety and health criteria for defining what constitutes responsible development of nanotechnology are needed. This article presents five criterion actions that should be practiced by decision-makers at the business and societal levels-if nanotechnology is to be developed responsibly. These include (1) anticipate, identify, and track potentially hazardous nanomaterials in the workplace; (2) assess workers' exposures to nanomaterials; (3) assess and communicate hazards and risks to workers; (4) manage occupational safety and health risks; and (5) foster the safe development of nanotechnology and realization of its societal and commercial benefits. All these criteria are necessary for responsible development to occur. Since it is early in the commercialization of nanotechnology, there are still many unknowns and concerns about nanomaterials. Therefore, it is prudent to treat them as potentially hazardous until sufficient toxicology, and exposure data are gathered for nanomaterial-specific hazard and risk assessments. In this emergent period, it is necessary to be clear about the extent of uncertainty and the need for prudent actions.

Overview of Risk Management for Engineered Nanomaterials.

Occupational exposure to engineered nanomaterials (ENMs) is considered a new and challenging occurrence. Preliminary information from laboratory studies indicates that workers exposed to some kinds of ENMs could be at risk of adverse health effects. To protect the nanomaterial workforce, a precautionary risk management approach is warranted and given the newness of ENMs and emergence of nanotechnology, a naturalistic view of risk management is useful. Employers have the primary responsibility for providing a safe and healthy workplace. This is achieved by identifying and managing risks which include recognition of hazards, assessing exposures, characterizing actual risk, and implementing measures to control those risks. Following traditional risk management models for nanomaterials is challenging because of uncertainties about the nature of hazards, issues in exposure assessment, questions about appropriate control methods, and lack of occupational exposure limits (OELs) or nano-specific regulations. In the absence of OELs specific for nanomaterials, a precautionary approach has been recommended in many countries. The precautionary approach entails minimizing exposures by using engineering controls and personal protective equipment (PPE). Generally, risk management utilizes the hierarchy of controls. Ideally, risk management for nanomaterials should be part of an enterprise-wide risk management program or system and this should include both risk control and a medical surveillance program that assesses the frequency of adverse effects among groups of workers exposed to nanomaterials. In some cases, the medical surveillance could include medical screening of individual workers to detect early signs of work-related illnesses. All medical surveillance should be used to assess the effectiveness of risk management; however, medical surveillance should be considered as a second line of defense to ensure that implemented risk management practices are effective.

Development of a fibre size-specific job-exposure matrix for airborne asbestos fibres.

OBJECTIVE: To develop a method for estimating fibre size-specific exposures to airborne asbestos dust for use in epidemiological investigations of exposure-response relations. METHODS: Archived membrane filter samples collected at a Charleston, South Carolina asbestos textile plant during 1964-8 were analysed by transmission electron microscopy (TEM) to determine the bivariate diameter/length distribution of airborne fibres by plant operation. The protocol used for these analyses was based on the direct transfer method published by the International Standards Organization (ISO), modified to enhance fibre size determinations, especially for long fibres. Procedures to adjust standard phase contrast microscopy (PCM) fibre concentration measures using the TEM data in a job-exposure matrix (JEM) were developed in order to estimate fibre size-specific exposures. RESULTS: A total of 84 airborne dust samples were used to measure diameter and length for over 18,000 fibres or fibre bundles. Consistent with previous studies, a small proportion of airborne fibres were longer than >5 microm in length, but the proportion varied considerably by plant operation (range 6.9% to 20.8%). The bivariate diameter/length distribution of airborne fibres was expressed as the proportion of fibres in 20 size-specific cells and this distribution demonstrated a relatively high degree of variability by plant operation. PCM adjustment factors also varied substantially across plant operations. CONCLUSIONS: These data provide new information concerning the airborne fibre characteristics for a previously studied textile facility. The TEM data demonstrate that the vast majority of airborne fibres inhaled by the workers were shorter than 5 mum in length, and thus not included in the PCM-based fibre counts. The TEM data were used to develop a new fibre size-specific JEM for use in an updated cohort mortality study to investigate the role of fibre dimension in the development of asbestos-related lung diseases.

Case-control study of lung cancer in civilian employees at the Portsmouth Naval Shipyard, Kittery, Maine.

Case-control analysis of deaths due to lung cancer (International Classification of Diseases, Eighth Revision, code 162) among persons who worked at the Portsmouth Naval Shipyard, Kittery, Maine, between 1952 and 1977 found elevated odds ratios for exposures to ionizing radiation, asbestos, and welding byproducts. The radiation-related excess was statistically significant in persons with cumulative lifetime exposures of 1.0-4.999 rem. When asbestos and welding histories were combined into a single risk factor, odds ratios for the combined exposure were significantly elevated for two of three duration-of-exposure categories examined. Further analysis of data on radiation exposure, controlling for exposures to asbestos and welding, found reductions in initial estimates of radiation risk at all levels of radiation exposure. This reduction suggests that radiation workers were more heavily exposed to asbestos and/or welding fumes than were other workers and that those exposures confounded the observed association between radiation and lung cancer. Analysis of mortality by time since first exposure to radiation revealed no pattern of progressive increase as latency increased. By contrast, odds ratios for asbestos/welding increased with latency. Data on cigarette smoking and socioeconomic status were not available. The results of this study do not preclude a possible association between radiation exposure at the Portsmouth Naval Shipyard and excess mortality from lung cancer. However, they provide no evidence in support of such a relation.

A retrospective cohort mortality study of males mining and milling attapulgite clay.

To evaluate the possible health effects of occupational exposure to a nonasbestos mineral fiber, a cohort of 2,302 males employed for at least 1 month between 1940 and 1975 at an attapulgite (clay fiber) mining and milling facility was followed through 1975. A significant deficit of mortality (SMR = 43, 90% CI 23-76) from nonmalignant respiratory disease (NMRD) was observed for the cohort based on age-, calendar year-, and race-specific rates for U.S. males. A marked deficit of NMRD was seen regardless of presumed dust exposure level, induction-latency period, or duration employed. A statistically significant excess of mortality from lung cancer was observed among whites (SMR = 193, 90% CI 121-293), but a deficit occurred among nonwhites (SMR = 53, 90% CI 21-112). Lung cancer risk in either race was not altered substantially with presumed dust exposure level, induction-latency period, or duration employed with one exception-those employed for at least 5 years in high-exposure-level jobs.

A case-control study of leukemia at a naval nuclear shipyard.

A matched case-control study was conducted of 53 leukemia deaths and of 212 controls within a previously studied cohort of 24,545 on-shore workers employed between January 1, 1952 and August 15, 1977 at the Portsmouth (New Hampshire) Naval Shipyard. The study sought to ascertain a priori whether there was an association between leukemia deaths and occupational exposure to either ionizing radiation or organic solvents. To obtain information on individual exposures, radiation dose histories and detailed work histories by job and shop were evaluated for each subject. No statistically significant associations were found either between ionizing radiation or presumed solvent exposure and myelogenous or lymphatic leukemia. However, when specific job categories and shops were examined without benefit of a priori hypotheses, two occupations, electrician and welder, were found to be associated with leukemia. For electricians, the Mantel-Haenszel odds ratio (ORMH) was significantly elevated for all leukemias (ORMH = 3.00, 95% confidence interval (CI) = 1.29-6.98), particularly for lymphatic leukemia (ORMH = 6.00, 95% CI = 1.47-24.45). For welders, the odds ratio was not significantly elevated for all leukemias (ORMH = 2.25, 95% CI = 0.92-5.53), but was significantly elevated for myeloid leukemia (ORMH = 3.83, 95% CI = 1.28-11.46). These findings persisted when potential confounders were adjusted by means of a conditional logistic regression model.

Cancer mortality at a Naval Nuclear Shipyard.

To evaluate a reported five-fold increase in leukaemia mortality among workers exposed to ionising radiation at Portsmouth (New Hampshire) Naval Shipyard (PNS), a retrospective cohort mortality study of all PNS civilian workers employed from 1952 to 1977 was done. Three subcohorts were identified: 7615 workers with radiation exposure of 0.001 to 91.414 rem (mean 2.779 rem, median 0.545 rem), 15 585 non-radiation workers, and 1345 workers selected for radiation work who received no measurable exposures. Vital status on 96% of the workers was ascertained and observed mortality due to all causes, all malignant neoplasms, and malignant neoplasms of the lymphatic and haematopoietic tissues, including leukaemia, was compared with that expected from mortality-rates for United States White males. Leukaemia mortality in radiation and non-radiation workers at PNS was also compared. Although the study had a power of greater than 99% to detect statistically a five-fold increase in leukaemia mortality among the radiation workers, and a power of 67% to detect a two-fold increase, there was no excess due to leukaemia or any other cause. The standardised mortality ratio for leukaemia among radiation workers was 84 (95% confidence interval, 34--174). There was no dose-response relation with radiation or any increased mortality in radiation over non-radiation workers. The study was, however, limited by short latency (time since first radiation); only 53% of the workers had less than 15 years' latency.