Electronic letters to:

Review:
Gideon Koren, Doreen Matsui, and Benoit Bailey
DEET-based insect repellents: safety implications for children and pregnant and lactating women
CMAJ 2003; 169: 209-212 [Abstract] [Full text] [PDF]
*eLetters: Submit a response to this article

Electronic letters published:

[Read eLetter] Missing Information on DEET
Robert D Nevin   (29 August 2003)
[Read eLetter] Soft on DEET
James I Moss   (13 August 2003)
[Read eLetter] Response to DEET-based insect repellents by G. Koren et al, Aug. 5, 2003; 169 (3)
Diana A. Somers, Cheryl Chaffey   (6 August 2003)

Missing Information on DEET 29 August 2003
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Robert D Nevin
Lockwood Clinic

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Re: Missing Information on DEET

robert.nevin{at}sympatico.ca Robert D Nevin

Dr. Koren failed to mention the results of animal trials involving dermal application of DEET.

Abdel-Rahman et al report diffuse neuronal cell death in the brains of adult rats after 6 days of daily dermal application of DEET compared to controls<1>. They conclude that motor deficits and learning and memory dysfunction could ensue from these changes.The impossibility of such a study in humans necessitates the consideration of this data in any risk analysis. Abou-Donia et al observed impaired sensorimotor performance in rats 30, 45, and 60 days following 60 days of daily dermal application of DEET in a controlled trial<2>.

It appears that Dr. Koren's review only deals with acute possible adverse reactions to DEET and that no long term controlled trials measuring neurological function in humans following dermal use of DEET have been done.

In light of the above and the low risk of death or serious illness in children from West Nile Virus in children[no deaths under the age of 24, out of 3698 cases of WNV in the USA<3>; no illness under the age of 26, out of 64 serious cases in Canada<4>], I have chosen frequent applications of soy bean oil for my children[a commercial product, "Bite Blocker", IS available in Canada and was purchased in June in Toronto].

<1>Abdel-Rahman A et al, Subchronic dermal application of DEET. Exp Neurol. 2001 Nov;172(1):153-71.

<2>Abou-Donia MB et al, Effects of daily dermal application of DEET... in rats. J Toxicol Environ Health A. 2001 APR.6;62(7):523-41.

<3>MMWR weekly Nov.22,2002/51(46);1049-1051.

<4>Pepperell C. et al, West Nile virus infection in 2002:... CMAJ. May27,2003;168(11).

Conflict of Interest:

None declared
Soft on DEET 13 August 2003
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James I Moss,
Toxicologist
University of FLorida

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Re: Soft on DEET

jimmoss{at}cox.net James I Moss

Are you aware that DEET toxicity in increased by pyridostigmine bromide(PB) in mice, rats, chickens, and insects? Considering the broad species range over which this is conserved, it is much more likely than not, that this alteration of DEET toxicity by is also conserved in humans.

PB is a drug that may easily be used by people who also use DEET. I would expect a review of the safety that mentions drug interactions, would at least mention this in passing. Why not?

James I. Moss Gainesville Florida

Moss, J.I. 1996. Synergism of Toxicity of N,N-Diethyl-m-toluamide to German Cockroaches (Othoptera: Blattellidae) by Hydrolytic Enzyme Inhibitors. J. Econ. Entomol. 89(5): 1151-1155.

McCain-Wilfred-C; Lee-Robyn; Johnson-Mark-S; Whaley-Janet-e; Fergusion-Jennifer-W; Beall-Patricia; Leach-Gleen. Acute oral toxicity study of pyridostigmine bromide, permethrin, and deet in the laboratory rat. J. Toxicol. Environ. Health; 50:2, 113-124, 1997

Abou-Donia-MB; Wilmarth-KR; Jensen-KF; Oehme-FW; Kurt-TL Neurotoxicity resulting from coexposure to pyridostigmine bromide, deet, and permethrin: implications of Gulf War chemical exposures.J-Toxicol- Environ-Health. 1996 May; 48(1): 35-56

Chaney, L., Moss, J., Mozingo, J., & A. Hume. 1997. Toxic interactions between pyridostigmine (PB), N,N-Diethyl-m-toluamide (DEET), adrenergic agents and caffeine. Toxicologist 36(1), P2, p21, #106.

Abou-Donia Mb, = Suliman Hb, Khan Wa, Abdel-Rahman Aa. Testicular Germ-Cell Apoptosis in Stressed Rats Following Combined Exposure to Pyridostigmine Bromide, N,N-Diethyl M-Toluamide (Deet), and Permethrin. J Toxicol Environ Health a 2003 Jan 10;66(1):57-73

Abdel-Rahman a, = Shetty a, Abou-Donia M. Disruption of the Blood- Brain Barrier and Neuronal Cell Death in Cingulate Cortex, Dentate Gyrus, Thalamus, and Hypothalamus in a Rat Model of Gulf-War Syndrome. Neurobiol Dis 2002 Aug;10(3):306
Response to DEET-based insect repellents by G. Koren et al, Aug. 5, 2003; 169 (3) 6 August 2003
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Diana A. Somers,
Director, Health Evaluation Division
PMRA, Health Canada,
Cheryl Chaffey

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Re: Response to DEET-based insect repellents by G. Koren et al, Aug. 5, 2003; 169 (3)

Diana_Somers{at}hc-sc.gc.ca Diana A. Somers, et al.

Health Canada was pleased to see the authors of the above article agree with our conclusions that repellents containing DEET are relatively safe when used as recommended. However, we would like to correct the impression generated by the article that Health Canada’s regulatory action in limiting DEET use in children (by concentration and frequency of use) was on the premise that young children are more prone than adults to the neurotoxic effects. Health Canada’s re-evaluation included a comprehensive evaluation of poison control data as well as the entire toxicological database combined with child-specific exposure assessments. The re-evaluation did not find evidence of increased sensitivity of children to DEET. However, the use of quantitative risk assessment methodology found lower margins of safety for children solely due to exposure data indicating that the dosage received by children was greater than that of adults (when corrected for body weight). The resulting label recommendations were determined based on this quantitative risk assessment.

For children aged 2 to 12 years, a 10% DEET product applied three times a day (with each application providing approximately 3 hours of protection) should provide sufficient protection for extended periods outside. We concur that common sense should prevail and that it may be prudent to reapply DEET after a session of swimming. With respect to children aged 6 months to 2 years, a maximum concentration of 10% DEET should be limited to one application per day and prolonged use should be avoided. This latter conclusion was reached by Health Canada in concert with the Canadian Paediatric Society.

While poison control statistics are a useful adjunct in confirming the safety of a product or identifying safety concerns, it should be remembered that they typically reflect acute overt outcomes and do not form the sole basis for health risk assessments in pesticide regulation. It is Health Canada’s position that regulatory restrictions on the use of DEET in the 6 month to 2 year age group is appropriate and protective when considering the entirety of the database.

Diana A. Somers, Ph.D. Director, Health Evaluation Division PMRA, Health Canada