发布者: katy | 发布时间: 2011-3-14 09:00| 查看数: 1076| 评论数: 0|

Immediate health risks for people living near Japan's Fukushima Daiichi nuclear plant appeared minimal Saturday, but experts cautioned that radioactive vapors could cause long-term problems ranging from birth defects to cancer if the situation worsens.

Radiation emitting from a nuclear plant, such as the one that became damaged following the earthquake in Japan and may be leaking vapors, is much more harmful to humans than radiation found in nature or x-rays, say experts. That is because the process that splits uranium using high heat creates over 100 new chemicals that can cause damage when they enter the air or food supply, said Joseph Mangano, executive director of nonprofit Radiation and Public Health Project, which researches the effect of radiation on public health.

'Once in the body these particles act like a wild bull in a china shop,' said Mr. Mangano. 'They bang around among the healthy cells and kill or injure them.'

Reports out of Japan suggest that the situation might not yet be harmful to the population's health. (Japanese officials say that the latest explosion at the nuclear power plant didn't come with a significant leakage of radiation.) Officials have said that the levels of radiation around the facility are eight times above normal, and 1,000 times more than normal in the facility's control room.

Based on a widely used definition of average normal exposure for humans ─360 millirems per year of radiation from rocks, cosmic rays and manmade sources─even those levels would be safe for humans, said Ron Chesser, director of the Center for Environmental Radiation Studies at Texas Tech University. Radiation doses would have to rise 250,000 times beyond those background levels to cause damage to human cells, he said.

Still, Dr. Chesser said that 'there is no doubt that there is a serious health situation there' because of how quickly problems could escalate. 'Every precaution needs to be taken.'

Health risks could include specific types of cancers, stillbirths and acute radiation syndrome if a full meltdown occurs, experts said. Of particular concern are three chemicals that can be released from nuclear facilities that mimic substances the body naturally uses, such as iodine and potassium. These chemicals are radioactive Iodine, Cesium and Strontium-90, said Dr. Chesser.

Problems to the thyroid are of particular concern. The thyroid gland doesn't differentiate between radioactive iodine and the normal kind, which it uses to produce hormones and function normally. Adolescents, whose bodies are quickly growing, are at particular risk. In addition, the effects can be long term: Dr. Chesser said that following the nuclear explosion in Chernobyl, thyroid cancers started to significantly increase only seven years after exposure.

To mitigate that risk, people can take iodine tablets that saturate the organ and make it unnecessary to absorb the radioactive iodine. Dr. Chesser also recommended that people stay indoors as much as possible.

Other health risks include bone cancer and compromised immune systems if the poisonous particles damage bone marrow. Fetuses and children are particularly susceptible to these risks since their immune systems are weaker, as are those of elderly people, experts said. Birth defects can arise after radiation exposure if the fetus is exposed to the toxic substances.

In an extreme case, people exposed to very high levels of radiation, such as after a nuclear bomb like the one dropped on Hiroshima, can suffer from radiation sickness, or acute radiation syndrome, said Mr. Mangano. Symptoms include fever, nausea, vomiting and skin rashes.

周六,住在日本福岛第一核电站(Fukushima Daiichi nuclear plant)附近的居民面临的健康风险目前看上去很小,但专家提醒说,如果形势恶化,放射性气体可能导致很多长期健康问题,包括先天性缺陷和癌症。

专家说,核电站泄漏的辐射对人类造成的伤害远甚于自然界的辐射或X射线。日本地震后受损的核电站就是一例,它可能泄漏放射性气体。研究辐射对公众健康影响的非盈利组织Radiation and Public Health Project的执行董事曼加诺(Joseph Mangano)解释说,这是因为利用高温分裂铀的过程会产生一百多种新的化学物质,这些化学物质进入空气或食物中会造成危害。



德州理工大学(Texas Tech University)环境辐射研究中心(Center for Environmental Radiation Studies)的主任切瑟(Ron Chesser)说,根据普遍使用的人类暴露于辐射中的平均正常值的定义,上述辐射水平对人类来说也是安全的。所谓平均正常值是指一个人每年从岩石、宇宙射线和人造放射源接触的辐射为360毫雷姆。切瑟说,辐射量要超过上述背景辐射的25万倍才会对人类造成伤害。








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