Expert Commentary

Nanomaterial Recommended Exposure Reduced

As the use of nanomaterials in consumer goods, medical devices, and other products continues to grow and the demand for such products continues to increase, so has the focus on the potential health effects to consumers and other users of products containing nanomaterials and to workers exposed to nanomaterials in the manufacturing process. Most recently, the National Institute for Occupational Safety and Health (NIOSH) reported the results of animal studies that show that certain types of nanomaterials can affect the lungs. In light of those studies, and in an attempt to further protect workers from suffering similar harmful effects, NIOSH lowered its recommended exposure levels and issued additional recommendations for employers related to the continued assessment of potential hazards as the hazards are still largely unknown.

July 2013

Pursuant to the Occupational Safety and Health Act of 1970, NIOSH is charged with recommending occupational safety and health standards and describing safe exposure levels and identifying potential harmful health effects. To that end, NIOSH issues Current Intelligence Bulletins (CIBs) to circulate scientific information regarding occupational hazards in an effort to educate all interested parties on potential health risks, including employers, workers, and federal agencies such as the Occupational Safety and Health Administration (OSHA). In its most recent CIB, Current Intelligence Bulletin 65,1 NIOSH discusses the results of animal studies indicating that carbon nanotubes and carbon nanofibers may pose a respiratory hazard to humans. This article focuses on NIOSH's recommendations and the steps employers and workers can take to implement best practices and manage potential risks as efficiently and effectively as possible.2

NIOSH's Findings in Connection with Animal Studies

CIB 65 focuses on NIOSH's systematic review of 54 laboratory animal studies involving rats and mice.3 Forty-four of the studies produced evidence that carbon nanotubes and nanofibers could cause pulmonary inflammation; 27 of the studies indicated granulomas, small areas of inflammation in tissue (commonly on the lungs) where the body attempts to wall off an infection; and in 25 of the studies, animals developed pulmonary fibrosis, scar tissue in the lungs that impedes respiratory function.4 NIOSH considers these studies to be relevant to potential human health risks because workers have suffered similar lung effects when exposed to respirable particulates of other materials in similarly dusty jobs.

Perhaps most significantly, NIOSH found that, in studies where carbon nanotubes were compared to other known fibrogenic materials (e.g., silica, asbestos, and ultrafine carbon black), the nanotubes were of similar or, in some cases, even greater potency. There are, however, some uncertainties where additional research is necessary to determine the extent to which the lung effects found in animals are caused by functional deficits.

NIOSH previously concluded in 2009 that available evidence was not sufficient to recommend specific medical tests for workers exposed to nanoparticles but promised to provide medical screening recommendations when relevant toxicological information became available. Based on its findings in CIB 65, particularly where the adverse effects in the subject animals developed quickly, persisted, and are detectable by medical testing, NIOSH has determined that protective action is warranted, and the animal studies provide toxicological evidence sufficient to support specific medical screening recommendations.

Medical Screening Recommendations and Recommended Working Lifetime Exposure Limit

NIOSH used the nonmalignant pulmonary data from the carbon nanotube animal studies as the basis for its recommended exposure limit (REL) because the available data on cancer and cardiovascular effects are not currently adequate for a quantitative risk assessment of inhalation exposure. Using that data, NIOSH found that, during a 45-year working lifetime, workers are potentially at risk of developing adverse lung effects if exposed to airborne carbon nanotubes. Based on that finding, NIOSH now recommends that workers be exposed to no more than 1 microgram of carbon/cubic meter of air during an 8-hour work shift for a duration of 45 years (1 µg/m3, 8-hour time-weighted average, 45 years). This is down from NIOSH's previous recommendation of 7 micrograms.5 CIB 65 also recommends Medical Screening and Surveillance Programs and more simple steps that employers and their workers can take to further protect from potential health effects.

The Medical Screening and Surveillance Program NIOSH recommends consists of an initial evaluation and subsequent, periodic evaluations. The initial evaluation should be conducted by a qualified healthcare professional and should, at a minimum, include the following:

  • A review of the worker's occupational and medical history

  • A physical examination with an emphasis on the respiratory system

  • A spirometry test (a lung function test)

  • A baseline chest X-ray

Periodic evaluations should then follow at regular intervals and at other appropriate times (e.g., after an accident or significant exposure or where symptoms occur). NIOSH recommends that periodic evaluations include an occupational and medical history update and X-rays, and a spirometry test should be conducted at least every 3 years and preferably more frequently. Based on the periodic testing, the medical provider should provide the worker with the results and advise of any relationships between the worker's conditions and occupational exposures and advise the employer with respect to whether the worker should be restricted from exposure and whether a worker's condition is in any way related to occupational exposures.

NIOSH also recommends that employers continually monitor their workers' exposure to nanomaterials in the workplace, which will allow them to detect problems and make appropriate changes at the earliest possible time to ensure worker safety and minimize the potential for harmful effects. Employers are encouraged to identify and characterize processes and job tasks where workers encounter bulk nanotubes or nanofibers, substitute, whenever possible, a less harmful substance than nanomaterials, ensure that workers are trained to check and use exposure controls such as ventilation systems, and routinely evaluate airborne exposures to ensure that control measures are working properly. It is also important to educate workers on when and how they may be exposed to nanomaterials, how they should protect against exposure, and how to clean up spills and decontaminate surfaces.


Although many of these recommendations seem like common sense, far too often, in an attempt to maximize productivity and revenues, both employers and workers ignore even the most simple safety measures. While it is true that carbon nanofibers and carbon nanotubes pose human health risks, it is far from clear, and there is much research still to be done. That said, the results of these animal studies and NIOSH's decrease in the recommended lifetime exposure limit should not be ignored. Any employer involved in the manufacture of carbon nanotubes or carbon nanofibers or the manufacture of products containing these specific nanomaterials should implement these NIOSH recommendations and revise risk management protocols as necessary. This will not only allow employers to stay ahead of the curve with respect to risk management but will also help to reduce litigation risk for alleged hazardous chemical exposure.

1CIB 65 is available at

2This article follows three previous articles published in this column, which discuss US and international standards for consumer and worker safety. (See "International Standards for Safety Data Sheets Are Coming for Manufactured Nanomaterials," published in October 2012; "Nanolabeling Standards Should Spur Regulatory Action," published in January 2013; and "OSHA and HSE Publications Promote Workplace Risk Management and Safety," published in April 2013.)

3NIOSH is careful to note and it is important to highlight here that, although the animal studies it reviewed produced adverse effects as a result of exposure to carbon nanotubes and carbon nanofibers and "there are well established correlations between results of animal studies and adverse effects in workers exposed to particulates and other air contaminants," NIOSH is not aware of any reports of adverse health effects in workers using or producing carbon nanotubes or nanofibers (CIB 65, Executive Summary, Overview).

5NIOSH originally proposed a REL of 7 µg/m3 in its 2010 draft CIB, Occupational Exposure to Carbon Nanotubes and Nanofibers.

*Adam Doherty is an associate at Prince Lobel Tye LLP in Boston. He is a member of the firm's Insurance and Reinsurance practice group, which represents insurers, reinsurers, captive insurers, managers, self-insurers, agents, and intermediaries located in the United States, Bermuda, the United Kingdom, and other European countries in a wide variety of matters. Mr. Doherty is also a member of the firm's Multidisciplinary Nanotechnology practice group, in which he focuses his practice on risk management, regulatory compliance, and litigation.

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