The Expanding Risk of Exposure to Nanoparticles in the Workplace

An emerging concern with worker health and safety in industrial settings is protecting workers from the byproducts of nanotechnology, the study and manipulation of matter that is between 1 and 100 nanometers in size. At these sizes (a nanometer being one billionth of a meter), substances can possess different properties from their larger counterparts, in part because the ratio of surface area to mass is much greater, leading to increased chemical reactivity, and in part because materials of such small size are subject to quantum effects, including unusual electronic, optical, or magnetic effects, that may not be present with materials of larger mass. Despite these differences, little research has been done on the potential harmful effects of nanoparticles, especially in occupational settings.

In their recent paper, Nanotoxicology and Exposure in the Occupational Setting (Occupational Diseases and Environmental Medicine, 3, 35-48), the authors review the current state of nanotechnology research in industrial settings, note the lack of industrial standards to regulate this area and protect worker safety, and call for further research on the topic. The authors note that while worldwide investment in nanotechnology in 2008 was estimated to be at about $30 billion, and projected to boom to about a $4 trillion market by 2018, relatively little money is being spent on researching the potential risks of this new technology.

Particular Risks Associated With Nanoparticles

Nanoparticles that enter the body through the respiratory system are a chief cause of concern, as smaller particles can penetrate deeper into lung tissue than can larger particles, leading to easier transport into the blood stream. The authors note that the effects of nanoparticles on the respiratory and cardiac systems seem to be more severe than the effects on other systems of the body, and thus those persons most at risk from exposure include those with chronic pulmonary obstructive diseases, cardiac diseases, asthma, and the elderly. Epidemiological studies also show that workers with prolonged exposure to nanoparticles from sources such as combustion engines or welding fumes suffer from higher rates of respiratory and cardiovascular diseases.

Given the relatively greater harm that may be caused through inhalation, the release of nanoparticles in the air as aerosols, where the particles are extremely mobile and can be inhaled easily, is an important concern. Nanoparticles subject to accidental release during manufacturing, maintenance, cleaning, or other procedures, may stay airborne for a long period of time. The authors note that “old pieces of equipment, liquids used for cleaning, and equipment used for cleaning may accidentally release nanoparticles into the environment unless special care is taken in their traceability and final storage. Additionally, in industrial processes that do not specifically use or create nanomaterials, nano-sized particles can be produced and released during activities like welding, smelting, [and] combustion ....”

While the authors note that oral ingestion of nanoparticles could be a significant path to exposure in occupational settings, through eating contaminated food or drink, swallowing inhaled particles, or hand-to-mouth transfer, current evidence suggests that nanoparticles that end up in the gastrointestinal tract tend to pass through the body quickly with limited absorption. Similarly, although existing studies were not focused on occupational settings, results indicate that damage to the liver from ingested nanoparticles tends to be limited to increased oxidation in the affected area, leading to short-term depletion of antioxidants without any real tissue damage.

Damage to human reproductive systems from nanoparticle exposure is another potential issue, with tests on mice showing adverse effects on sperm stem cells, embryonic stem cells, and midbrain cells. At least one study showed that the motility of human sperm could be reduced by exposure to gold nanoparticles, and exposure to diesel exhaust has been shown to produce changes in gene expression for gonad development. The authors note, however, that most existing studies involve animal testing and in vitro experimentation rather than direct human testing, supporting the need for more research in this area.

As noted by the authors of this study, the biological effects of nanoparticles are greatly influenced by their particular physical and chemical characteristics, which can vary greatly depending on how the particles are produced. In addition, nanoparticle properties may change “depending on the environment ..., transport and mechanisms of accumulation, degradation, and release.” These differences can complicate any effort to compare the effects of nanoparticles that are produced from different sources, as the resulting particles can be very different.

Impact on Occupational Practices

The authors point to several occupational hazards that may increase the risk of exposure to nanoparticles, including:

•  working with nanomaterials in liquids during pouring and mixing operations without adequate safeguards such as the use of gloves;

•  generating nanoparticles in non-enclosed areas;

•  handling powders of nanomaterials;

•  performing maintenance on equipment and processes used to produce nanomaterials and cleaning spills and waste material containing nanoparticles;

•  cleaning dust collection systems that capture nanoparticles; and

•  engaging in machining, sanding, drilling, and other mechanical disruptions of materials containing nanoparticles.

While the authors note that further research on occupational exposures is needed and may point to more refined protections, suggested measures that may currently protect against unnecessary occupational exposure might include:

•  evaluating any nanoparticle hazard based on the physical and chemical property data, toxicology, and health-effects data currently available;

•  assessing occupational tasks to determine exposure risks;

•  establishing good work practices by training workers in proper nanomaterial handling;

•  and installing engineering controls such as exhaust ventilation at locations where exposure might occur;

•  utilizing appropriate personal protective gear such as clothing, gloves, or respirators; and

•  evaluating exposures to ensure that control measures were being used and were working properly.

They also note that exhaust ventilation systems using high-efficiency particulate air (HEPA) filters are known to effectively catch nanoparticles, and the use of HEPA vacuums and wet wiping of exposed areas, along with common sense practices such as preventing food or beverage consumption in areas exposed to nanoparticles and providing hand-washing and showering facilities and areas for changing clothes, can also be effective in preventing exposures.

The authors point out that while regulatory occupational exposure limits may exist for non-nanoparticle substances, no airborne exposure limits exist specifically for their nanoparticle analogues. Given that nanoparticles may behave differently when ingested, the exposure limits provided for non-nanoparticle masses may not be sufficient to protect worker health against the risks associated with nanoparticle exposure. Thus, they caution that an employer’s decision on whether to provide workers with respirators “should be based on professional judgment that takes into account toxicity information, exposure measurement data, and the frequency and likelihood of the worker’s exposure.”

Similarly, the authors point out that while there are no current guidelines to aid in selecting clothing to combat skin exposure to nanoparticles, some clothing standards do test with nanoscale particles and therefore some clothing may provide an indication of effectiveness in protecting against exposure.

Regulatory and Standardization Momentum

Although little to no standards or regulation of nanoparticle exposure have existed in the past, the authors point to some promising developments in this area that are worth noting. For example, the European Union has implemented the Registration, Evaluation, and Authorization of Chemicals Regulation (REACH), which requires manufacturers, importers, and other producers to file dossiers on substances greater than a specified tonnage in order to access markets in the European Union. While REACH does not specifically reference nanomaterials, there appears to be no reason currently to exclude such materials from coverage.

The authors also note that standards for testing and measuring the effects of nanoparticles are either recently adopted or pending from many organizations world wide, including the International Organization for Standardization, the American Society of Mechanical Engineering, the American Society for Testing and Materials, the British Standards Institution, the Institute of Electrical and Electronics Engineer, and the National Institute of Standards and Technology.

Conclusion

The authors of Nanotoxicology and Exposure in the Occupational Setting point out that, while “nanotechnology offers the promise of unprecedented scientific advancement for many sectors,” this relatively nascent field also brings with it “new challenges to understanding, predicting, and managing potential safety and health risks to workers.” In light of the current lack of conclusive data about the effects of exposure to nanoparticles on the human body, the authors recommend that all nanomaterials be considered potentially hazardous and call for more research on the specific effects of nanoparticle exposure.

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