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Potential Human Health Risks of Nanomaterials

Joseph Clark | March 1, 2011

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Nanomaterial tubes

Open any magazine or newspaper, flip through science programs on television, or scan the Internet for new technologies, and you will likely come across an article, show, or website that deals with nanotechnology in some form or another. Nanotechnology is frequently hailed as "the next big thing" or, even more ambitiously, "the next big thing that's already here." But what is nanotechnology, and why should we care about it?

Although no standardized definition of nanotechnology exists yet, a reasonable starting point can be found on the National Nanotechnology Initiative's (NNI) website: 1

Nanotechnology is the understanding and control of matter at dimensions between approximately 1 and 100 nanometers, where unique phenomena enable novel applications.

It is the "unique phenomena" that make nanotechnology so important and give it staying power, because nanoenabled products often perform better than their non-nano counterparts. Industry is aware of nano's value and, according to Woodrow Wilson Institute's Project on Emerging Nanotechnologies, the number of nanoenabled consumer products exceeds 1,000. (The inventory is located at Clothing and cosmetics top the inventory, but there are many other products on the list, including appliances, cars, computers, and food, and drink. New products are entering the market at a rate of around 3–4 per week on average.

But, the promise of "new and better" is not without pitfalls, and there is uncertainty as to whether exposure to nanoparticles through dermal contact, inhalation, or ingestion can cause bodily injury. It is this potential toxicity that is a source of concern.

Human Exposure

Nanomaterials are becoming ubiquitous in medicine (e.g., molecular targeted therapies, diagnostic imaging), consumer goods (e.g., cosmetics, electronics, baby products), and building materials (e.g., concrete, steel, windows). The physiochemical nature of these materials may vary depending on the intended purpose—the therapeutic value, structural support, thermal property, cosmetic appeal, durability, etc.—of the engineered product. For example, nanomaterials such as carbon nanotubes and SiO2 nanoparticles are often used to add mechanical strength and durability, TiO2 nanoparticles are used to increase the degree of hydration, and FeO3 nanoparticles are used for abrasion resistance. 2

Individuals may have access to new products containing nanomaterials almost every day. 3 The purported benefits of these "new and improved" products is often clearly stated on product packaging and advertisements. Examples include waterproof pants, stain-resistant shirts, socks that eliminate foot odor, pacifiers that fight bacteria, and computers that run faster, inter alia. However, the potential human health risks following long-term exposure to some products are not certain, as there is generally a lack of exposure data to evaluate if these products are safely performing their intended purpose. 4 For example, there may be a paucity of information regarding potential risks to an infant who spends several hours per day exposed to nanomaterials in an engineered product, such as a bottle or pacifier.

Our understanding of materials science, coupled with our ability to rapidly implement nanomaterials into engineered products, may have outpaced our analytical ability to accurately quantify human exposure. Currently, there are no universally accepted measurement procedures—analytical methods—established for measuring human exposure to nanomaterials precisely. This may be ascribed to the unique physicochemical properties of nanomaterials as compared to bulk materials, such as soil or dust, or volatile chemicals, such as benzene, PAHs, and TCE. The currently employed analytical methods are dynamic, mostly involving a modification of conventional methods for quantifying micro-sized materials. 5

Human Health Hazards and Risk

Compared to the chemical risk assessment process, where hazards are generally identified as a function of an organism's adverse response to a particular mass of a chemical agent (a dose), characterizing the hazards of nanomaterials has been problematic. This is largely due to the many features that may contribute to the toxicity of nanomaterials. For example, an organism's response to a particular nanomaterial may be related to the mass of the administered dose, or it may be related to other factors, including the number of particles, shape, electrical charge, and coating, or a combination of physiochemical characteristics. Currently, there is no consensus within the scientific community on what characteristic may be the most important in elucidating this dose-response relationship for each type of nanomaterial. This lack of agreement is understandable, given that studies evaluating the health effects of nanomaterials show a range of findings (i.e., dose-response relationships) and underscore the inappropriate generalization of responses across all types of nanomaterials.

While some authors have opined that frequent use of nanomaterials may be "the next asbestos" (in terms of observations of large cohorts of individuals with lung and pleural diseases), careful analysis suggests that this is unlikely. Unlike much of the historical asbestos exposure, nanomaterials in engineered products are generally not "bioavailable," i.e., freely available to cause biological damage in target organs, when incorporated into end-user materials. For example, sepiolite clay (a DuPont™ manufactured nanomaterial referred to as DNM-1) is initially manufactured as powder, and the raw product is incorporated into a pellet encapsulated in a PET (polyethylene terephthalate) resin for commercial applications, such as frozen food trays 6. The probability of widespread exposure to the powder is substantially decreased after incorporation into the polymer resin, thus mitigating any potential health hazard.

Government/NGO Recommendations

Most governmental agencies and nongovernmental organizations involved in standardization have been relatively slow in promulgating regulations and standards relating to nanotechnology. However, the National Institute of Occupational Safety and Health (NIOSH), the leading federal agency conducting research and providing guidance on the occupational safety and health implications and applications of nanotechnology, released a publication in March 2009 entitled, "Approaches to Safe Nanotechnology: Managing the Health and Safety Concerns Associated with Engineered Nanomaterials," which sets forth a series of recommended best practices for occupational safety and health. Additionally, in November 2010, NIOSH issued, for public comment by February 18, 2011, a bulletin addressing exposure to carbon nanotubes in the workplace. Of paramount importance is NIOSH's recommended exposure limit (REL); this represents the first time NIOSH has provided a hard number relating to nanoparticles exposure. In arriving at the REL, NIOSH stated, "[u]ntil improved sampling and analytical methods can be developed, and until data become available to determine if an alternative exposure metric to mass may be more biologically relevant, NIOSH is recommending a REL of 7 μg/m3 elemental carbon (EC) as an 8-hr TWA respirable mass airborne concentration."

On the environmental front, the U.S. Environmental Protection Agency (EPA) has not only classified certain nanomaterials as "emerging contaminants" but has also issued Significant New Use Rules (SNURs) under the Toxic Substances Control Act (TSCA) 7 for single and multi-walled carbon nanotubes. 8 The EPA has been more active than other government agencies, and it is likely that it will be the vanguard of nanotechnology regulation for the foreseeable future.

In addition to government agencies, consensus standards organizations, such as the International Organization for Standardization (ISO), the American Society for Testing and Materials (ASTM), and the American National Standards Institute (ANSI) (in conjunction with ISO) are formulating guidelines for the safe handling, use, and disposal of nanomaterials by workers and consumers. To date, progress has been slow, but the standards that do exist currently are a helpful foundation upon which to build more specific standards.

Potential Liability

Whenever there is risk, there is always a potential for liability; in the case of nanotechnology, it is not a case of whether liability will arise, but when. Below is a sample of some potential sources of liability for stakeholders.

In the workplace, in the absence of a health or safety standard, the General Duty Clause at Section 5(a)(1)of the Occupational Safety and Health Act of 1970 delineates an employer's responsibilities. The clause mandates that each employer "furnish to each of his employees employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm to his employees." A General Duty Clause violation occurs when a condition or activity in the workplace presents a hazard that could have been eliminated or materially reduced and is likely to cause death or serious physical harm to an employee.

As the EPA develops more rules and regulations, it is certain that liability will become an issue under various statutes, including the TSCA, the Clean Water Act, and the Clean Air Act. In fact, the EPA has indicated a willingness to enforce existing rules, and in at least one case, has brought a claim under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) against a manufacturer for failing to register products with nanoenabled antimicrobial coatings. The EPA's position was that products which kill or repel bacteria or germs are pesticides and must therefore be tested and registered. Ultimately, the claim was settled, and the manufacturer paid a significant sum—$208,000.

Claims have been nonexistent on the consumer front, but the small size of nanoparticles, coupled with potential deleterious effects, will certainly lead to litigation in the products liability arena. Whether we will see asbestos level/mass tort litigations is unknown, but both manufacturers and insurers should stay on top of potential liability now.


There are many existing risk management practices that would be prudent to employ based on the current state of knowledge of the potential risks of nanomaterials. Simple good work practices (exposure controls, proper worker education, personal protective equipment, record keeping) are highly advised when manufacturers or industries are working with nanomaterials. Since the regulatory landscape for this burgeoning new material is dynamic, it is advisable to implement adequate cleanup and disposal protocols when dealing with nanomaterials with uncharacterized hazards. For example, use stringent Food and Drug Administration (FDA) guidance when faced with a material with no existing standards. All risk management practices should be verified and documented using standard health and safety audits (e.g., internal record audits, along with consultant verified records). Finally, select individuals in each organization ("compliance officers") that are tasked to stay abreast of the developing science and its impact on contemporary workplace practices for your insureds.

Note: In future articles, we will provide a more in-depth review of each of the subject areas summarized above. Namely, we will examine possible routes of environmental (i.e., occupational and domestic) exposure, the potential for human health injury in the workplace, contemporary governmental and non-government organization (NGO) recommendations and standards, the possible liability of nanomaterials use, and "state-of-the-science" recommendations culled from recently published scientific papers.

Dr. Marc A. Nascarella is a toxicologist at Gradient, an environmental consulting company, and specializes in comprehensive chemical evaluations and human health risk assessment. Dr. Barbara D. Beck is a toxicologist and risk assessor, and directs Gradient's nanotechnology, toxicology, and risk assessment practices. Both contributed to this article.

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1 According to the NNI website at, the NNI was established in 2001 to coordinate Federal nanotechnology research and development. It consists of the individual and cooperative nanotechnology-related activities of 25 federal agencies with a range of research and regulatory roles and responsibilities. Thirteen of the participating agencies have research and development budgets that relate to nanotechnology, with the reported NNI budget representing the collective sum of these.
2 Lee et al., Nanomaterials in the Construction Industry: A Review of Their Applications and Environmental Health and Safety Considerations, 4 ACS Nano. 3580 (2010).
3 Project on Emerging Nanotechnologies (PEN), The Consumer Product Safety Commission and Nanotechnology (August 2008),
4 Thomas H. Moore, Statement of Commissioner Thomas H. Moore Submitted to the Subcommittee on Consumer Affairs, Insurance, and Automotive Safety Senate Committee on Commerce, Science, and Transportation (March 21, 2007),
5 Park et al., Exposure Assessment of Engineered Nanomaterials in the Workplace, 26 KOREAN J. CHEM. ENG. 1630 (2009).
6 DuPont™, Nano Risk Framework Output Worksheet for: DuPont™ Crystar® 6920 PET poly-(ethylene terephthalate) Resin with Sepiolite Clay, Pangel S-9 as an Encapsulated Nanodispersed Filler (July 23, 2008),
7 TSCA was enacted to regulate the importation, production, use in commerce, and disposal of specified chemicals with the intent to ensure the safe use of such chemicals within the American workplaces and in commerce.
8 The Federal Register notice is available at:; the rules went into effect on October 18, 2010.