"We live in a society exquisitely dependent on science and technology, in which hardly anyone knows anything about science and technology." The words of Carl Sagan, the American astronomer famous for popularizing science, describe well the global situation with regard to electromagnetic radiation. Daily we are immersed in the electromagnetic fields (EMFs) that provide so many conveniences in our lives: computer monitors, power lines, mobile phones. But they may well also be providing us with serious, even lethal, health problems.
During the past 30 years, about 25,000 essays on the biological and medical effects of EMFs have been published. Although it is widely felt that research in this area is far from sufficient, we have in fact accumulated more data than in many other traditional subjects, including some branches of chemistry.
In 1982, Samuel Milham conducted a study in the US state of Washington on the effects of large electrical and magnetic fields on workers. Milham, an occupational health physician, wrote in the New England Journal of Medicine that he found more leukemia-related deaths in men whose work brought them in contact with electrical and magnetic fields, such as employees of utility companies.
More recently, the Institute of Cure and Prevention of Occupational Disease of Hunan Province completed a study on the effects of radiation on technicians who have close contact with large EMFs. The comparison group was office workers exposed only to low-level EMFs in far smaller fields.
The results show that technicians suffered insomnia, heart palpitations or hair loss at far higher rates than the other group. Their cardiogram abnormity rate was 37.8 percent, compared with 16.1 percent in the comparison group.
The technicians also suffered poorer eyesight, probably due to the heat effects of microwave. Since human eye is filled with liquid that can easily absorb microwave radiation, their temperature may become elevated with exposure to EMFs. It is believed that this may solidify proteins, causing the eye's lens to develop "microwave cataracts."
In addition, more than 64 studies in the United States and Europe have linked chronic exposure to magnetic fields, such as those from power lines and computer monitors, to unusually high incidences of cancer, leukemia, and tumors. EMFs are linked to headaches, cataracts, heart problems, stress, fatigue, nausea, insomnia, Alzheimer's disease, chest pain, and significantly higher than expected rates of leukemia. Animal experiments have shown higher rates of birth defects and miscarriages.
Many Chinese ask the question, "Are we safe?" TV and radio transmission towers, power lines and mobile phone base stations cast shadows over virtually every corner in big cities such as Beijing, Shanghai and Guangzhou. Although evidence is incomplete and inconsistent, it is clear that there is a correlation of some sort between microwaves and health.
Exposure to high-level EMFs has been shown to be harmful, but there is no definite answer concerning moderate levels.
Laboratory studies on humans exposed to moderate EMFs have showed no observable changes in blood pressure, body temperature, sleep, appetite or physical functions. Other studies have found no mood and behavior changes in human subjects.
But according to environmental supervision data, one percent of China's mobile phone base stations exceed the environmental management standard for EMF density (8μW/cm² ), and some top the national standard of 40μW/ cm² . For instance, among the 3,000 base stations in the Beijing area owned by China Mobile and China Unicom, six exceed the standard; of the 5,000 base stations in Liaoning Province, the number rises to 10.
"China has stricter microwave standards than developed countries like the United States. However, the density of EMFs in Chinese cities is higher than that in other countries. Microwave radiation in developed countries is much lower than the set standard," said Cao Zhaojin, an electromagnetic radiation expert from the Environment Supervision Institute of the Academy of Preventive Medical Science.
"According to current research, it is hard to distinguish between harmful and non-harmful radiation. A low radiation level does not mean it is safe. That is why developed countries demand radiation in public places must be much lower than the standard."
Obviously China's big cities are actually teetering on the rim of a radiation hazard.
The issue of mobile phones as a source of danger has been hotly debated.
Mobile phones use microwaves to transmit signals. The emission power is between 0.25 and 2 W (the old standard being 3 to 5 W). But because mobile phones are operated in such close proximity to -- actually in contact with -- the body of the user, the radiation is great.
Cao noted that both Chinese and foreign experts have measured electromagnetic density around mobile phone antennas. In most cases, the figure varies from 10 to several hundred μW/ cm² . When a phone is in use, that figure can reach as high as 1,000 μW/ cm² .
If a user uses a 900 MHz phone, the temperature of his ear and adjacent skin will rise significantly, as much as 2.5 degrees Celsius. Heat under the level of the skin may affect brain activity and the neural system.
Studies on cat, rat, and chick brain cells show that low-frequency electromagnetic radiation interacts with brain activity and could cause a host of negative symptoms, from heightened stress and depression, slowed reaction and learning disabilities to miscarriages, fetal deformities and cancer.
In 1996, the World Health Organization (WHO) established the International Electromagnetic Fields (EMF) Project to address the health issues associated with exposure to EMFs. A comprehensive report is expected to be complete between 2005 and 2006.
The WHO's International Agency for Research on Cancer (IARC) has recently concluded the first step in WHO's health risk assessment process by classifying EMFs. This year, IARC expects to have adequate data to complete its assessment.
(China.org.cn by Li Liangdu, July 6, 2004 )
