Certain insect repellents: neurotoxicity

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http://www.medicalpost.com/mpcontent/article.jsp?content=20040705_185104_3164

 

CPS: Case of DEET overuse prompts warning

 

Certain insect repellents will no longer be sold due

to neurotoxicity concerns

 

By Terry Murray

 

MONTREAL – A case of neurotoxicity due to overuse of a

DEET-containing insect repellent has prompted an

Ottawa doctor to remind physicians of guidelines for

the product's use.

 

In fact, re-evaluation of DEET-containing products by

the federal Pest Management Regulatory Agency (PMRA)

in 2001, in part to ensure extra protection for

children, resulted in some products no longer being

marketed while others will not be sold after this

year.

 

In a poster session of the CPS meeting, Dr. Heather

MacDonnell, a clinical fellow in academic pediatrics

at the University of Ottawa, reported the case of a

20-year-old with Down syndrome who developed mild

encephalopathy after overusing a DEET-containing

insecticide.

 

While at camp for two weeks, the man liberally applied

the 21% DEET product over his entire body, including

mucous membranes, for several hours a day. His

sleeping bag was impregnated with the product,

resulting in additional inhalation and transdermal

exposure.

 

His cabin mates noticed that his level of

consciousness declined to the point that he collapsed

on the cabin floor. His clothes were washed and he was

showered thoroughly, and he recovered.

 

" There are guidelines for the safe use of DEET in

children, " Dr. MacDonnell said in an interview,

referring to those issued by the CPS last year on West

Nile virus. (They are available on the CPS Web site:

www.cps.ca.)

 

They include means of non-chemical protection from

mosquito bites, but also recommend that DEET products

be used with caution and under supervision. The CPS

guidelines are:

 

• for children under six months of age, do not use

insect repellents containing DEET;

 

• for those ages six months to two years, use a

maximum of one application of up to 10% DEET daily,

applied sparingly to the skin, but not the face or

hands;

 

• for those ages two to 12, up to three daily

applications per day of maximum 10% DEET; and

 

• for those 12 and over, products containing up to 30%

DEET can be used.

 

The different concentrations of DEET refer not to the

product's effectiveness, but to the duration of

protection that can be expected, Dr. MacDonnell said.

For example, the approximate protection time of 5%

DEET is two hours, 10% is three hours, 15% is five

hours and 30% is six hours.

 

In its 2001 review, PMRA decided that products

containing DEET concentrations above 30% would no

longer be approved for sale in Canada, based on a

human health risk assessment that considered daily

application of DEET over a prolonged period of time.

Sale of existing products will continue to the end of

the this year to allow them to be used up, thus

preventing disposal problems, the PMRA decision said.

If they're concerned, individuals and families can

discard any of the higher-concentration products they

have with their regular household garbage, the agency

added.

 

PMRA ruled the sale of products that contained both

DEET and sunscreen should be discontinued at the end

of 2003 " because of the incompatible label

instructions regarding methods of application " —that

insect repellents should be applied sparingly but

sunscreen should be used liberally and frequently.

 

Dr. MacDonnell said she hopes that " parental education

and proper product labelling will decrease the

incidence of serious side-effects associated with DEET

application in the future. "