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Welcome to PSR's Environmental Health Policy Institute, where we ask questions -- then we ask the experts to answer them. Join us as physicians, health professionals, and environmental health experts share their ideas, inspiration, and analysis about toxic chemicals and environmental health policy.

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Risk Assessment: An Inadequate Tool to Assess Health Threats to Nail Salon Workers from Chemicals in the Workplace

by Catherine A. Porter, JD

Quantitative risk assessments evaluate potential adverse health effects posed by exposure to harmful chemicals.  It is used to inform policy decisions by legislators and government agencies, including the EPA to protect health. Risk assessment includes four steps: 1) hazard assessment; 2) exposure assessment; 3) dose-response assessment; and 4) risk characterization.

Despite its wide use, risk assessment has been criticized for its failure to adequately reflect the real world where exposures to hazardous chemicals take place. In its most recent evaluation of the risk assessment process, the National Research Council recommended improvement in several areas, including:  eliminating the assumption that there is a “safe” threshold for non-cancer toxicants; better accounting for vulnerabilities and variabilities among and between populations; rethinking the general rule of “the dose makes the poison;” incorporating cumulative exposures; and recognizing non-chemical stressors and other background factors.[i]  The health threats to nail salon workers offer a case in point.

In the U.S., nail salon workers are largely Asian women of reproductive age with large Vietnamese and Korean populations. Individuals in this work sector are often Limited English Proficient, potentially creating barriers to communication with customers as well as understanding information on safety and regulatory requirements.  The median wage nationwide is $19, 220. [ii]

Everyday, workers in the nail salon industry are exposed to hazardous chemicals.  Toluene, for example, is a common ingredient in nail polish, polish thinner, glue, and other products.  It is a reproductive and development toxicant under California’s Prop 65, and has been linked to spontaneous abortions. [iii]  It is also a neurotoxicant.  Chronic exposure to low levels of toluene damages the central nervous system (brain) of workers.[iv]  Similar effects are seen in animals. [v]

Risk assessment has assumed that there is always a concentration below which exposures are "safe." [vi] As a consequence, non-cancer effects such as reproductive, developmental, neurological, or other serious harm “have been underemphasized, especially in benefit-cost analyses.” [vii]

Risk assessment has ignored vulnerabilities and variabilities across and within populations.[viii]  According to a recent Committee Opinion of the American College of Obstetricians and Gynecologists, “[t]he effects of low-dose exposure to an environmental contaminant may be quite different based on vulnerabilities, such as the underlying health status of the population and the presence of additional or ‘background’ environmental exposure.” [ix]  In the case of toluene, at least some Asian groups metabolize toluene differently from others.[x]  This means that unmetabolized toluene, which is the form of toluene that is harmful, remains in many nail salon workers’ bodies longer than in others with greater potential for harm.

Risk assessment has generally assumed “the dose makes the poison.” Evidence now demonstrates that low dose exposures, as well as the timing of exposure, can be critical variables when assessing many environmental contaminants.  Additionally, exposures in nail salons are experienced in a way that is not easily captured in typical air monitoring measurements.  Due to the nature of the business and how nail services are provided, chemical exposures can be episodic; they may be of shorter duration but of a higher and hazardous level, yet when averaged over an 8-hour time period can appear to be "safe."

Risk assessments usually focus on one chemical at a time, ignoring potential additive effects from other exposures.  In nail salons, workers are exposed simultaneously not only to toluene, but also to dibutyl phthalate and methyl ethyl ketone, both of which are also developmental toxicants.[xi]

Risk assessments generally ignore non-chemical stressors, but should be “expanded to include consideration of non-chemical stressors…and background risk factors.”[xii]   The health effects from exposure to environmental chemicals “can be exacerbated by injustice, poverty, neighborhood quality, housing quality, psychosocial stress, and nutritional status.” [xiii] According to one study, immigrants experiencing language barriers “were generally more stressed, especially at the beginning of their lives as immigrants. The combined effect of stress and a language barrier led to poorer health in these immigrants.”[xiv]  Risk assessment cannot consistently capture or evaluate these real-world complexities within the nail salon community.

Risk assessment cannot be the only game in town. Risk assessment will continue to be utilized, especially when it comes to evaluating alternatives, but it should not be the only tool for determining what kind of policy decisions are needed to best protect all communities.  A more precautionary approach should also be utilized -- where the question is not “how much harm can we allow” but rather “how much harm can we prevent?”


[i] National Academy of Sciences, National Research Council, Report in Brief, Science and Decisions – Advancing Risk Assessment (2008) [hereinafter Report in Brief] (accessed 11/12/2013)

[iii] Ng TP, Foo SC, Yoong T. Risk of spontaneous abortion in workers exposed to toluene. Br J Ind Med 49 (1992): 804-808

[vi] Report in Brief, p. 3.

[vii] Id.

[viii] Id.

[ix] American College of Obstetricians and Gynecologists, Committee Opinion, Number 575 [hereinafter ACOG Opinion) (accessed 11/12/2013) October 2013, citing National Research Council. Science and decisions: advancing risk assessment. Washington, DC: National Academies Press; 2009. 

[x] Kawamoto T, Murata K, Koga M, et al.  1994.  Distribution of urinary hippuric acid concentrations by ALDH2 genotype.  Occup Environ Med 51:817-821.

[xi]  OEHHA, Chemicals known to the State to cause cancer or reproductive toxicity. Di-n- butyl phthalate (DBP), p. 9 (accessed 11/13/2013); OEHHA.  2008.  Acute toxicity summary.  Methyl ethyl ketone.  Appendix D.2, page 180.  Acute RELs and toxicity summaries using the previous version of the Hot Spots Risk Assessment Guidelines (OEEHHA 1999). (accessed November 13, 2013)

[xii] Report in Brief, p. 4.

[xiii] ACOG Opinion, citing Adamkiewicz G, Zota AR, Fabian MP, Chahine T, Julien R, Spengler JD, et al. Moving environmental justice indoors: understanding structural influences on residential exposure patterns in low-income communities. Am J Public Health 2011;101(suppl 1):S238–45 (abstract);  Morello-Frosch R, Zuk M, Jerrett M, Shamasunder B, Kyle AD. Understanding the cumulative impacts of inequalities in environmental health: implications for policy. Health Aff 2011;30:879–87.  (abstract)

[xiv] Journal of Immigrant and Minority Health, 2009 Dec;11(6):446-52. doi: 10.1007/s10903-008-9200-0. Epub 2008 Oct 21. Stress-associated poor health among adult immigrants with a language barrier in the United States. (abstract)

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