What is the disadvantage of Pyrothroid-impregnated nets

No allergist anywhere in the world has proposed the use of such nets for allergic or asthmatic patients to control house dust mites present in large numbers in mattresses or pillows. Anyhow do not use permethrin-treated products if you have an allergy to chrysanthemums or are hypersensitive to chemicals. The use of pyrethroid containing products in the home environment may do more harm for chemical-sensitive individuals. There are several other reasons that argue against the use of such netting in the home. The netting is placed over the top part of the mattress and the argument is that when the dust mites come in contact at night with the net they would be killed by the chemical. There is only one study conducted with normal individuals using the net. The net had the ability to kill a proportion of the dust mites in the mattress but the mites continued to proliferate in the mattress throughout the period of the study over several months showing that the net does not totally eliminate the mites from the mattress. The accumulation of dead mites and their fecal pellets on the mattress may be a hazard for patients with asthma since this high load of dust mite allergen could trigger an attack. The impregnated-net is marketed with the suggestion that it is effective for a period of 24 months but no study exists to substantiate this point. According to World Health Organization sources the half-life of pyrethroid impregnated-net is about 8 months and therefore the chemical is effective for that period only. After this period the net must be recharged with the chemical or the netting replaced with a new one. Obviously replacing the product every 6 to 8 months becomes an expensive option but recharging with the chemical may be a cheaper option. However, there are other reasons to avoid exposure to pyrethroid chemicals because of health concerns particularly for the young. Naturally derived pyrethrins are well recognized sensitizers and people can develop hypersensitive reactions to them. Similar sensitizing potential of synthetic pyrethroids has also been noted. Outbreak of several cases of urticaria occurring in children due to pyrethroid chemical has been reported in the literature (Vet Hum Toxicol. 1999, 41:92-3). Moreover recent experimental studies show that some pyrethroids, including permethrin, are endocrine-modulating chemicals and can accumulate in breast milk. On lactational delivery to the newborn the chemicals can accumulate in the brain causing activity-dependent gene expressions in cerebellar neuronal cells to be repressed. These studies suggest that lactational exposure to pyrethroids might negatively affect the postnatal development of the mammalian brain (Arch Toxicol. 2002,76:392-7). A 45 year old female animal keeper who was exposed to pyrethroid insecticides over a period of 13 years at her workplace in activities (such as feeding, maintenance of hygienic conditions, and application of insecticides) developed what is called the pyrethroid syndrome. Clinical history revealed mainly neurologic and allergy like symptoms which developed in a progressive manner through exposure to pyrethroid chemicals over years. She also developed pain syndrome in muscles and joints. These symptoms had been apparent for about 5 years. Furthermore, the patient suffered from abnormalities of the neural behavior (e.g., loss of strength and performance, abnormal tiredness, loss of interest, sensation of coldness, dysphoria, heart arrhythmia, rapid pulse, malfunction of memory and concentration, nausea, headache, decreased olfactory sensitivity, and low blood pressure), hair loss, hypothyreosis, and vitiligo. The animal keeper was incapable of work due to the severity of the complaints and required regular medication for her condition. Recently, in a report by BBC News Online the insecticide permethrin was shown to cause a series of chemical changes in brain that could lead to the development of Parkinson’s disease (research conducted by Virginia Polytechnic University and presented at the American Chemical Society). Researchers studied changes in brain chemicals in mice exposed to different levels of permethrin, often used on clothing and netting to kill and repel ticks and mosquitoes. The study found that exposure to the insecticide resulted in reduced levels of the chemical transmitter dopamine in the brains of the mice. It also found that permethrin led to increased production of a protein that is a major component of fibrous tangles found in the brains of people with Parkinson’s disease. Just a small dose of the insecticide was enough to cause these chemical changes in the brains of the experimental mice.