Public Safety Considerations for Lindane
Concerns about lindane and cancer risks have related largely to past agricultural uses and occupational exposure to persistently high concentrations of lindane (gamma-hexachlorocyclohexane, or HCH). Health and environmental risks have also resulted from the agricultural use of technical-grade HCH—a more toxic mixture of different HCH chemicals that has not been permitted for use in the U.S. since the 1970s.1-3 (See 2006 EPA RED on Agricultural Lindane)
In contrast, lindane medications, which contain a highly purified form of gamma-HCH, are used in relatively small amounts and in low concentration, typically as one-time treatments.4,5 (See Healthcare vs. Agricultural Uses of Lindane) To date, there has been no established link between pharmaceutical-grade lindane and cancer in humans, despite over 50 years of medical use.3,6-8
Findings of a large epidemiologic study of lindane carcinogenic (ie, cancer-causing) effects:6
- Conducted at Kaiser Permanente Medical Care Programme—a 50–year-old health maintenance organization in Oakland, California
- Based on a 143,594-patient database and up to 21 years of patient follow-up
Study conclusions reported in 1997:
“There is still no persuasive evidence from studies of humans that lindane, as ordinarily used clinically, is carcinogenic in humans.”6
- In 2001, the EPA downgraded lindane’s carcinogenic classification to the same low-level rating as other commonly prescribed first-line scabies and lice medications, including permethrin (ingredient in Nix®), pyrethrin (ingredient in Rid®) and malathion (ingredient in Ovide®)7-9
- The change followed a reevaluation of all available scientific evidence on lindane, including the results of newer studies requested by the EPA’s Cancer Assessment Review Committee after determining older studies to be flawed
- The Committee concluded that the evidence did not warrant additional assessment of the cancer risk of lindane in humans—no further actions were deemed necessary7
- EPA Cancer Assessment Review Committee Conclusions on Lindane
“The Committee recommended that quantification of human cancer risk is not required”7
World Health Organization (WHO) perspective on lindane cancer-causing potential:10
- In 2004, the Joint Committee on Pesticide Residues—an international groups of scientific experts coordinated through the WHO and Food and Agricultural Organization (FAO) of the United Nations—concluded that lindane was not likely to pose a cancer risk to humans10
- Similarly, they noted that, “In an epidemiological study designed to assess the potential association between breast cancer and exposure to chlorinated pesticides, no correlation with lindane was found.”10
- Conclusion of the WHO/FAO Joint Meeting on Pesticide Residues (JMPR) on Lindane and Cancer
“In the absence of genotoxicity [ability to damage DNA] and on the basis of the weight of the evidence from the studies of carcinogenicity, JMPR has concluded that lindane is not likely to pose a carcinogenic risk to humans.”10
Many of the safety concerns about hexachlorocyclohexane (HCH) have related to alpha-, beta-, and technical-grade HCH
It is important to appreciate the differences between the different forms of HCH because they all have different properties, uses and safety profiles.
- Alpha- and beta-HCH are notably the most toxic forms of HCH7
- Technical-grade HCH—a mixture of different isomers consisting predominantly of alpha-HCH—is also considered unsafe and is no longer used agriculturally in the U.S. (but is still used in other parts of the world)2
- Alpha-, beta-, and technical-grade HCH have never been used in medicine
Alpha- and beta-HCH have greater cancer-causing potential:7
- Alpha-HCH is classified as a “probable human carcinogen” as is technical-grade HCH
- Beta-HCH is classified as a “possible human carcinogen”
- In contrast, gamma-HCH (lindane) is classified as having only “Suggestive evidence of carcinogenicity, but not sufficient to assess human carcinogenic potential.”7
- This conclusion was based on the occurrence of non-cancerous (i.e., benign) lung tumors in just one sex of one species of mice— specifically female CD-1 mice—which are genetically predisposed to developing lung tumors7,11
- Note also that these research mice were fed high oral doses of lindane over prolonged periods of time, which is not how topical lindane medications are used
- This finding has not been replicated in other animal studies nor has it been demonstrated in humans
Please See Important Safety Information on Lindane
- Commission for Environmental Cooperation. The North American Regional Action Plan (NARAP) on Lindane and Other Hexachlorocyclohexane (HCH) Isomers. 2005. Available at: http://www.cec.org/files/PDF/POLLUTANTS/Lindane-NARAP-Public-Comment_en.pdf.
- Commission for Environmental Cooperation. Decision Document on Lindane Under the Process for Identifying Candidate Substances for Regional Action Under the Sound Management of Chemicals Initiative. April 19, 2000. Available at: http://www.cec.org/files/pdf/POLLUTANTS/linddd_en.pdf.
- U.S. Environmental Protection Agency (EPA). Lindane Reregistration Eligibility Decision (RED). 2002. Available at: http://www.lindane.com/pdf/lindane_epa_2002.pdf.
- Lindane lotion, USP, 1% prescribing information. Updated March 28, 2003. Available at: http://www.accessdata.fda.gov/drugsatfda_docs/label/2003/006309lotionlbl.pdf.
- Lindane shampoo, USP, 1% prescribing information. Updated March 28, 2003. Available at: http://www.accessdata.fda.gov/drugsatfda_docs/label/2003/006309shampoolbl.pdf.
- Friedman GD. Lindane and cancer in humans: A false alarm? Pharmacoepidemiol and Drug Saf. 1997;6:129-134.
- U.S. Environmental Protection Agency (EPA). Evaluation of the Carcinogenic Potential of Lindane, PC. Code: 009001. 2001. Available at: http://www.lindane.com/pdf/EPA_Cancer_Assessment_of_Lindane2001.pdf.
- U.S. Environmental Protection Agency (EPA). ). A Consultation on the Proposed Health Effects Division Classification of the Human Carcinogenic Potential of Malathion. 2000. Available at: http://www.epa.gov/oscpmont/sap/meetings/2000/august/committee.pdf
- PAN Pesticides Database. Permethrin-identification, ecological toxicity and regulatory information. Available at: http://www.pesticideinfo.org/Detail_Chemical.jsp?Rec_Id=PC35397.
- World Health Organization. Lindane in Drinking Water: Background Document for Development of WHO Guidelines for Drinking-Water Quality. 2004. Available at: http://www.who.int/water_sanitation_health/dwq/chemicals/lindanesum.pdf.
- Manenti G, Galbiati F, Noci S, et al. Outbred CD-1 mice carry the susceptibility allele at the pulmonary adenoma susceptibility 1 (Pas1) locus. Carcinogenesis. 2003;24(6):1143-1148. Online version available at: http://carcin.oxfordjournals.org/cgi/content/full/24/6/1143