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作者：Fran Lowry  
出處：WebMD醫學新聞

　　April 16, 2010 — 世界衛生組織(WHO)今天發表一篇聲明，提出冰島艾雅法拉火山(Mt. Eyjafjallajokull)爆發所產生的灰塵微粒，可能會對健康產生風險。
　　
　　WHO表示，如果這些火山灰沉降到較低的大氣層或者濃度升高，氣喘與其他慢性呼吸道症狀如肺氣腫或支氣管炎的病患會比較容易受到影響。火山爆發的灰雲可能包括非常細微的玻璃顆粒，但是只要它維持在較高的大氣層，就不太可能引起不良的健康影響。
　　
　　WHO公共衛生與環境部的Maria Neira醫師在聲明中表示，微粒物質根據它的直徑而定，小於10微米(μm)的小顆粒更危險，因為它們會侵犯到肺臟深部。
　　
　　根據WHO表示，專家們正在分析火山灰，估計約有25%的顆粒小於10微米。
　　
　　Neira醫師指出，因為風向與大氣溫度不同，各國的灰燼濃度有所差異，我們的建議是聽從當地公共衛生官方對個人狀況的最佳指引，如果到戶外時發現喉嚨和肺部受到刺激、流鼻水或眼睛癢，就應該回到室內且減少戶外活動。
　　
　　她也建議，如果空氣污染情形惡化，氣喘和其他慢性呼吸道疾病患者應避免費力的活動。
　　
　　加拿大多倫多大學地質學家Pierre Robin博士向Medscape Medical News表示，火山爆發在冰島很常見，但是我們從未聽說過。
　　
　　因為三個巧合而造成這次浩劫，第一，在冰河之下爆發，產生的蒸氣吹動岩漿或玻璃碎片、高達11公里而進入大氣層。第二，噴射氣流通過並且帶走這些細微顆粒，將它們帶往世界各地，這個噴射氣流或許已經涵蓋了莫斯科。第三，爆炸發生在世界上空中交通最繁忙的區域，如果它發生在澳洲，它會擾亂當地的空中交通，但是不會對其他地方有所影響。
　　
　　Robin博士表示，噴射氣流將繼續帶著這些細微玻璃碎片造成的火山灰燼達數週之久。
　　
　　他指出，艾雅法拉火山依舊活躍，但是難以得知是否會繼續有全球影響。或許再2天左右，空中交通受阻將可解除。這個爆發或許會持續2年，但是這些巧合、蒸氣爆炸的噴射氣流或許不會再出現，我們真的不知道。
　　
　　賓州匹茲堡大學氣喘研究中心共同負責人Fernando Holguin醫師向Medscape Medical News表示，來自火山爆發的許多微粒物質實際上在上部大氣層過濾，傷害程度不像汽車廢氣的微粒物質，因為它們(指火山灰)比較大。
　　
　　他相信，任何健康風險不只會影響居住在靠近爆發區域的人，也會影響居住在數千英里之遠的人。
　　
　　他表示，住在靠近火山爆發區域的人，曝露於較高濃度的顆粒與大量的二氧化硫，這是相當強的呼吸道刺激物，可能會引起暫時性支氣管收縮，特別是如果你有氣喘和COPD的話，但是，我不認為居住在離火山爆發區域數千英里遠的人顧慮會更多。
　　
　　比較危險的是那些排自汽機車、小於2.5微米的細微顆粒，這些對心血管和呼吸道健康有傷害，因為它們迅速沉積在呼吸道且進入血流。


Volcanic Ash From Iceland May Have Health Consequences

By Fran Lowry
Medscape Medical News

April 16, 2010 — The World Health Organization (WHO) today issued a statement warning about a potential health risk due to fine ash particles from the ongoing eruption of Mt. Eyjafjallajokull in Iceland.

People with asthma and other chronic respiratory conditions such as emphysema or bronchitis may be more susceptible to irritation if the ash is in the lower atmosphere or in high concentrations. The ash cloud from the explosion contains very tiny particles of glass, but as long as it remains in the upper atmosphere, it is unlikely to cause untoward health effects, says the WHO.

"Particulate matter is identified according to its diameter," said Maria Neira, MD, Director of Public Health and Environment Department at the WHO, in a statement. "The small particulates less than 10 microns in size are more dangerous because they can penetrate deeper into the lungs."

Experts are analyzing the ash and estimates show that approximately 25% of the particles are less than 10 microns in size, according to the WHO.

"Since the ash concentration may vary from country to country depending on the wind and air temperatures, our advice is to listen to local public health officials for the best guidance for individual situations," Dr. Neira added. "If people are outside and notice irritation in their throat and lungs, a runny nose or itchy eyes, they should return indoors and limit their outdoor activities."

She also advised that people with asthma and other chronic respiratory diseases should avoid strenuous exercise if air pollution increases.

Volcanic eruptions are common in Iceland, but we never hear about them, Pierre Robin, PhD, a geologist from the University of Toronto in Canada, told Medscape Medical News.

"This one has created havoc because of 3 coincidences. Number 1, it erupted under a glacier, and the resulting steam explosion blew the magma, or shards of glass, up to 11 kilometers into the air. Number 2, the jet stream was going by and picked up these tiny particles, and is now carrying them around the world. The jet stream is probably over Moscow already. Number 3, the explosion took place in an area of the world that has the most dense air traffic. If this had occurred in Australia, for example, it would have disrupted air traffic there, but not anywhere else."

The jet stream will continue to carry the tiny shards of glass that make up the volcanic ash for several weeks, Dr. Robin said.

Mt. Eyjafjallajokull remains active, but it is hard to know whether this will continue to have a global effect, he added. "Maybe in 2 days the air traffic interdiction will cease. The eruption might go on for 2 years but the coincidence, or perfect storm of steam explosion and jet stream proximity may never arise again. We just don't know."

Fernando Holguin, MD, MPH, codirector of the University of Pittsburgh Asthma Institute in Pennsylvania, told Medscape Medical News that much of the particulate matter that comes from volcanic eruptions are actually filtered in the upper atmosphere and are not as harmful as the particulate matter that comes from car exhaust, for example, because they are larger.

He believes that any health risks would affect people living relatively close to the eruption and that the risk to people living thousands of miles away is slight.

"Individuals in close proximity to a volcanic eruption get exposed to high concentrations of particles and also large amounts of sulfur dioxide, which is a very powerful airway irritant and can cause transient bronchial constriction, especially if you have asthma and COPD," he said. "But I don't think that would be of much concern to people who are thousands of miles away from the site of a volcanic eruption."

Much more dangerous are the fine particles that are emitted from motor vehicles that are smaller than 2.5 microns. These are harmful to cardiovascular and respiratory health because they are readily deposited in the airways and cross into the blood stream, he said.