Mosquito Repellents and Their Dangers

Bloodsucking mosquitoes are enemy No. 1 in the summer months. They wake us from slumber, which is difficult enough to come by in the heat, and cover arms and legs in unsightly, itchy bites.

Yet Korea is still safer than other regions, where an annual 2-3 million people die from diseases transmitted by mosquitoes including malaria, dengue fever and Japanese encephalitis. And the vectors for these diseases are expected to propagate further and grow more aggressive as global warming proceeds.

Repellents, then, are a must, but here too caution is advisable. The Chosun Ilbo looks at the available options.

◆ Mosquito Coils

This is made by mixing the pesticide allethrin, which mosquitoes hate, with wood powder. They are molded into a solid form and dyed in the trademark green. But safety is an issue. The Environment Ministry in 2006 banned the use of the carcinogenic dye malachite green and said companies had taken the substance out of their coil products.

But we cannot rest assured. Last year, Yang Won-ho, a professor of occupational health at Catholic University of Daegu, and his team tested burning mosquito coils imported from Vietnam and Malaysia in a closed room. In the experiment, one coil produced an amount of the carcinogen formaldehyde found in anywhere between two to 22 cigarettes as well as minute dust particles produced when burning 41-56 cigarettes.

All mosquito coils sold in Korea are imported. Yang said more problematic than the pesticide or carcinogen content which is less than 1 percent of what constitutes the coil is the other 99 percent. He advises against burning the coil too long indoors, citing study results that children can develop asthma when they are exposed to the smoke for longer periods.

◆ Aerosols

The main ingredient of powerful insecticide aerosols is pyrathroid, which kills the creatures by paralyzing their nervous system. The biggest problem with aerosols is that people use them excessively.

Lim Young-wook, vice director of Yonsei University's Institute for Environmental Research, quotes a U.S. study that found aerosol is more often absorbed into the body indirectly through utensils and hands than direct inhalation. Skin, food, utensils and toys exposed to aerosol must be rinsed with soap immediately.

◆ Electric mats

Electric mats are also based on pyrathroid. Mats are less toxic than mosquito coils but are more often used indoors as they have no scent or smoke, which can cause allergic rhinitis, asthma, sneezing, headache, tinnitus, nausea or in extreme cases coma. The mats must be placed within 2 m to have effect. It's rumored to decrease sperm count, but pyrathroid content in the density of only 1/700 is unlikely to have the effect.

◆ Repellents

There are also products such as lotions to be applied on the body that contains "deet" which scares away mosquitoes. Dr. Kim Soon-il at NaturoBiotech says "Deet was developed by the U.S. military in the 1950s and accounts for over 90 percent of the repellent market."

But after findings that deet can adversely affect childbirth, brain nerves and heart ailments, the U.S. Centers for Disease Control and Prevention in 2005 recommended the use of picaridin or the natural lemon eucalyptus instead of deet.

The Korea Food and Drug Administration has also banned the sale of products containing more than 30 percent of deet in line with standards in advanced countries. Yet repellents with higher deet density have longer and more powerful effect. Children under 12 are advised to use repellents with less than 10 percent deet. They should not be used too much or for too long near the eye, mouth, wounds or tanned skin and should be rinsed with soap when returning from outdoors.

◆ Fluorescent Lamps and Others

Ultraviolet rays of a special wavelength range can also attract and eradicate the mosquitoes with heat. Though no chemicals are involved, there is a risk of electric shock or leak. The Korean Agency for Technology Standards under the Ministry of Knowledge Economy has recently surveyed the safety of seven repellent fluorescent lamps in the market. Four of them had no protection against electric shocks and their product certification was canceled.

Also popular are wearable bands and patches scented with natural ingredients like lavender and citronella. They are easy to use and don't have any side effects, but are not as effective as the others.