Permethrin is safe, effective insecticideA letter May 31...


June 06, 1996

Permethrin is safe, effective insecticide

A letter May 31 in The Sun criticized the use of the insecticide permethrin to control adult mosquitoes.

Several statements in the letter concern me because they are misleading. I wish to address those concerns and to provide information about permethrin.

Permethrin is registered as a mosquito control insecticide by the U.S. Environmental Protection Agency and approved for use in residential areas, recreational areas, golf courses, woodlands, campgrounds, etc.

Permethrin is referred to as a synthetic pyrethroid insecticide because, while synthetically made, it resembles naturally occurring chemicals with insecticidal properties, called pyrethroids.

Pyrethroids are produced by chrysanthemum plants and are one of the oldest known classes of organic insecticides. Pyrethroids work by paralyzing the nervous system of insects. Pyrethroids are widely used for home pest control, agricultural pest control, mosquito control and other uses.

Permethrin has low toxicity to mammals. Mammalian livers efficiently metabolize permethrin to nontoxic metabolites, which are quickly excreted and do not persist in body tissues. Permethrin is practically non-toxic to birds. Permethrin does not block, or inhibit, cholinesterase enzymes.

Permethrin can be toxic to fish. To safeguard fish and other aquatic resources, the Maryland Department of Agriculture adheres strictly to the label requirement to not apply permethrin within 100 feet of rivers, ponds, lakes or streams. The rate used to control adult mosquitoes in Maryland (0.003 pounds of permethrin per acre) is below the level known to cause fish mortality.

The letter writer expressed concern that permethrin is a very long-lasting insecticide. It is true that one use of permethrin -- spraying clothing for protection against ticks -- results in persistence for several days because a relatively large dose is applied directly to clothing. About five times more permethrin is applied to one outfit of clothes for tick protection than is applied to one acre for mosquito control.

Due to the low rate of application and the method used to apply it, there is no residual effect of permethrin as a result of mosquito control spraying.

The letter writer goes on to state that the permethrin product he uses requires a respirator be worn when spraying clothing for tick control and that the clothing must dry for 24 hours before wearing. I recommend he change brands of permethrin.

The permethrin I use for tick control suggests treating a clothing outfit until it is moist (no respirator required) and to allow it to dry 2 hours (4 hours under humid conditions) before wearing.

The letter states that permethrin was used in the Annapolis area for mosquito control in 1995, and that people complained of dizziness, nausea and difficulty in breathing as a result. Permethrin was not used in Maryland for mosquito control last year. Hence, the reported impacts to human health as a result of spraying permethrin near Annapolis for mosquito control are not factual.

The May 31 letter did not portray an accurate representation of the mosquito control program. The staff of the mosquito control program in the state Department of Agriculture works hard to provide a service and do so with no adverse effect to the environment, and to the enhancement, not detriment, of human health.

Cyrus R. Lesser


The writer is chief of the mosquito control section, Maryland Department of Agriculture.

Embargo hurts Cubans as much as the Iraqis

I was appalled reading the article ''U.S. reportedly to permit bids on Iraqi oil,'' June 2.

The U.S. apparently is backing what they like to call ''oil-for-food'' to help the Iraqi people suffering under a trade embargo. How much more contradictory can the United States get?

Take the embargo on Cuba. For the last five years, the United Nations has declared it illegal. This year there were only three countries to vote for it, the U.S., Israel and Afghanistan.

It's a well-known fact that the U.S. is involved in an illegal trade embargo. The most recent example was the computer mayhem.

This involved the U.S. confiscating computers that were going to be sent to Cuban medical authorities. They said the reason was that the U.S. was not sure they were for medical purposes, but perhaps they were for ''trade.''

The U.S. declared war on Iraq six years ago and said it was because of the tyranny of Saddam Hussein. How do you explain the fact that the U.S. was dealing arms to Iraq until six weeks before declaring war?

The truth was that the gulf war was a war of oil and eradicating political dissidents, not to protect people, with the possible exception of the U.S. petroleum industry.

When will the U.S. grow up and understand that Cuba is not a threat in any way, shape or form?

It is a country with a different political system. One with health care for everyone, but they can't get the medical supplies they need because of the U.S. illegal embargo.

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