March 2, 2007

Light At Night Is Dangerous To Health

Night life under electric lighting may cause serious behavioral disorders and physical diseases including cancer, according to a specialist team led of the Professor N.N. Pertov Scientific Research Institute of Oncology, Russian Ministry of Healthcare, and Petrozavodsk State University, who have been investigating the effects of night-time illumination on people's health for several years.

The researchers summarized findings of their own investigations and extensive foreign experience, medical statistics and data of experiments carried out on rodents. Permanent bright light suppresses synthesis of melatonin, the hormone that impacts the endocrine system work and prevents cancerous growth formation and development.

Light pollution has become almost an integral part of contemporary life. Bright electric light pours on the people who have to work on night shifts, pilots and stewardesses, who often travel from one time zone to another, and inhabitants of the North (where white nights take place in summer). Normal functioning in humans requires regular changing of day and night, light and darkness. In the dark, the epiphysis (the pineal gland) synthesizes the melatonin hormone, but the influence of light at night hours suppresses this synthesis. Melatonin is also a well-known biological blocker of malignant neoplasms.

The more intense the night-time light, the stronger it suppresses the melatonin synthesis. Some people are more sensitive to night-time illumination's action than others, for example, women are generally more sensitive than men. Light pollution can cause premature reproductive system ageing, and increase the risk of breast cancer and large intestine cancer in women. Night workers and pilots more often suffer from large intestine or rectal cancers. In addition, irregular light can causes sleep disturbance, gastrointestinal and cardiovascular diseases, metabolic derangements and, possibly increase the likelihood of developing diabetes.

This is confirmed by results of experiments with rodents, which react to permanent light in the same way as humans do. Cancerous growth occurs more often with mice and rats under permanent light conditions, being more susceptible to chemical carcinogens and malignant cell inoculation. Mice suffering from cancer die more often in light pollution conditions than in controls with undisturbed day and night. A similar phenomenon is also recorded by clinicians: according to some observations, patients with large intestine cancer who retain the 24-hour rhythm of activity live longer than the patients with disrupted rhythms.

Cancerous growth behavior is closely connected with the melatonin concentration in the serum. It usually changes depending on the time of the day, but with oncological patients and laboratory animals, the diurnal rhythm of melatonin in serum is significantly disrupted, and its concentration is below normal.


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