J. Toxico1.-Cut. & Ocular Toxicul., 19(4), 173-176 (2000)

LETTER TO THE EDITOR

MISLEADING MALATHION SAFETY STATEMENT BY CONSUM€R REPORTS MAGAZINE*

To the Editor:

In the February, 2000, issue of Consumer Reports,’ a brief editorial appeared with the title “Head lice update: Scratch some remedies.” Among other points made, the author of the article cited research recently conducted at the Harvard School of Public Health showing that head lice are becoming resistant to the leading over-the- counter product, NIX, which contains the active ingredient permethrin. In addition, the author also raised concerns about a prescription-only drug called Ovide, con- taining the active ingredient malathion. The article stated:

The malathion contained in a single Ovide treatment can be up to 30 times the recog- nized safe one-time dose for a young child. Yet according to the product’s label, no tests have been done to measure how much of the malathion is absorbed through the scalp, nor is it known whether Ovide is safe for children under 6.

Having had some experience with Ovide and pharmaceutical-grade malathion, I found the statement “30 times the recognized one-time dose . . .” highly question- able. Other safety opinions expressed in that Consumer Reports article took off from that same statement, which made them suspect as well.

1 was concerned for two reasons. First, there is a serious and growing head lice health problem in the United States and other parts of the world because lice, are developing resistance to permethrin-based products (such as Nix). Second, the Centers for Disease Control, which are concerned about the growing resistance prob-

* Ediror’s note: This Letter to the Editor is in response to our “Commentary: Malathion Wrongly Maligned,” which appeared in issue 19(2&3), pp, 103-104, of the Journal.

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174 LETTER TO THE EDITOR

lem, made a statement to the Food and Drug Administration (FDA) supporting the effort of the manufacturer of Ovide, Medicis Pharmaceutical Company, to market Ovide as a public service. Since Ovide had already been approved by FDA as being safe and effective, Medicis was able to follow through quickly and make Ovide available to the general public.

I called a colleague who is an expert in the field of toxicology for a second opinion concerning the Consumer Reports statement about Ovide’s safety. We dis- cussed that statement at length, and my initial impressions about it being misleading were reinforced.

I then called Consumer Reports at their Yonkers, NY, location to find out the basis of that questionable statement. After several back and forth phone conversa- tions, including one with a supervisor in their customer relations department, I was told that the reference for the above-quoted statement was obtained by the author of the article from a web site sponsored by the Environmental Protection Agency (EPA).

The same supervisor also told me that the author’s statement was based upon the acute oral reference dose (RfD) value for malathion, that the formula used in their calculations was:

Weight of a child (20 kg) X RfD for malathion = the RfD for a child ( I )

mg malathion in a bottle Of ‘‘IDE = x times the safe dose for a child, (2) RfD for a child and that the author had calculated a value of 29.5, which was rounded off to “30 times the recognized . . .’’

This was how the author arrived at the “30 times the recognized, . .” conclu- sion, Although mathematically correct according to the formula used, the toxicologi- cal logic and the conclusions drawn from it are seriously juwed for the following reasons.

First, an RfD is an estimate of the daily exposure of a toxicant to the human population that is likely to be without an adverse ejfect after continual lifetime expo- sure at that level. RfD values are typically based upon ingestion or inhalation of a material. In contrast, Ovide is applied topically to the hair. As a result, only some of the product touches the scalp. Studies using excised human skin,“ radiolabeled malathion in human volunteers,.‘ and normal or exaggerated application to the scalp of humans6 have shown that adsorption through the skin is low (in the 1.6-9% range or less), in contrast to that expected via the oral/systemic route.

There is a very big difference between toxicity values determined when an agent is given orally and those determined when it is applied topically. Furthermore, the Ovide product is typically applied only once or only occasionally. Thus, exposure to malathion via topical application is certainly orders of magnitudes less than a lifetime of repeated exposure.

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LETTER TO THE EDITOR 175

None of the above information was factored into the Consumer Repurts analysis and conclusions.

A second point is that Ovide contains the relatively pure USP, pharmaceutical- grade of malathion rather than the insecticide or industrial-grade, which contains impurities associated with much of malathion’s toxicity. Consumer Reports based their conclusions about malathion’s safety (RfD) on industrial-grade, not pharmaceu- tical-grade malathion.

Thus, all of the above elements are critical to the accurate assessment of safety, and all were assessed erroneously in the Consumer Reports article.

T have frequently seen both nontechnical and technical individuals or groups in the media or on the Internet draw scientific conclusions that are misleading because of several reasons: (1) they have not done their homework, (2) they are not profes- sionally trained to reach balanced and scientifically objective conclusions, and/or (3) they choose not to be objective and balanced because they have a specific agenda. The result is unnecessary misinformation that often ends up confusing the general public or polarizing them with false information.

Had the author of the Consumer Reports article done further homework, the following could also have been determined. In the United Kingdom, the scientific regulatory authorities have approved the use of 0.5% malathion-based head lice prod- ucts for approximately 30 years. Because of their safety record, many of these prod- u c t ~ ~ are available to consumers over-the-counter. In addition, malathion-based prod- ucts have been approved for use on infants down to the age of 6 months in the United Kingdom because of the agent’s long history of safe and effective use in the United Kingdom (and other countries). In the United States, Ovide is approved for children above the age of 6 years. I have recently learned that FDA is expecting US data to confirm the United Kingdom’s safety recommendation for children under 6 years of age.

In addition, a solid scientific article published in 1999 by Dennis and Lee6 showed that topical use of malathion-based head lice products, including one formula similar to Ovide, were found to be quite safe when applied to normal and/or abraded scalp, even when use was exaggerated through multiple applications. The authors state that they “found no evidence of a clinical effect on either plasma or erythrocyte cholinesterase activity with malathion-containing head lice preparations when they were applied in accordance with the instructions for use to the heads of healthy volunteers.” If an unusual level of malathion had penetrated the scalp area and en- tered the general circulation, acetylcholinesterase activity would have been adversely affected. This did not occur, even with exaggerated use.

Finally, the author of the Consumer Reports article, as an objective reporter seeking the facts and presenting them in a balanced manner, should have contacted Medicis, the manufacturer of Ovide, before publishing the article. The author did not do so.

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176 LETTER TO THE EDITOR

In summary, we again have an instance in which a consumer magazine has misled their large audience with the wrong conclusions based upon poor homework. In this case, there is a disservice to the community because of the growing resistance among head lice to existing treatments, and the FDA-approved, pharmaceutical grade of malathion appears to be needed to help overcome this serious and health problem.

Nicholas F. Schmidt, Ph. D. Bolton Landing, NY

References

1. Head lice update: Scratch some remedies, Consumer Reports, 2: 49, 2000. 2. J. Rowland, Personal communication Environmental Protection Agency. 3. Seton Scholl Healthcare (Oldham, UK), (Suleo-M Lotion, Derbac-M Liquid, Prioderm Lotion,

Prioderm Cream Shampoo. 4. J. L. McCullough, In vitro percutaneous absorption and distribution studies of malathion formu-

lations in human cadaver skin, Final Report, University of California, Irvine, UCI Study #HAS

5. R. C. Wester, H. I. Maibach, A. W. Bucks, and R. H. Guy, Malathion percutaneous absorption after repeated administration to man, Toxicol. Appl. Phamacol. 68: 116-1 19, 1983.

6. G. A. Dennis and P. N. Lee, A phase I volunteer study to establish the degree of absorption and effect on cholinesterase activity of four head lice preparations containing malathion, C h . Plzarma- codyn. 18(2): 102-115, 1999.

99-1, 1999.

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