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手機(jī)使用率居高不下,為何腦癌發(fā)病率卻在下降?

手機(jī)使用率居高不下,為何腦癌發(fā)病率卻在下降?

Scott Woolley 2011-06-09
雖然從1990年至今,手機(jī)輻射量增加了500倍,但腦癌發(fā)病率卻有所下降。

????上世紀(jì)80年代,隨著手機(jī)在美國(guó)投入使用,低頻率輻射開(kāi)始影響人類(lèi)大腦,腦癌發(fā)病率隨之緩慢上升。在80年代初,每年每百萬(wàn)美國(guó)人中有63人被醫(yī)生診斷為腦癌,到1990年,這一數(shù)字上升到70人/百萬(wàn)人。而此時(shí)手機(jī)使用才剛剛開(kāi)始普及。

????手機(jī)和腦癌發(fā)病率之間的相關(guān)性似乎肯定會(huì)呈上升趨勢(shì),然而奇怪的是,從1991年開(kāi)始,腦癌發(fā)病率突然調(diào)頭開(kāi)始緩慢下降。2008年,即美國(guó)國(guó)家癌癥研究院(National Cancer Institute)有記錄的最后一年,每百萬(wàn)美國(guó)人中只有65人患有腦癌。

????在這20年里,隨著手機(jī)用戶(hù)數(shù)的瘋狂增長(zhǎng),美國(guó)人大腦所受到的手機(jī)輻射量增加了500倍。如今的美國(guó)手機(jī)用戶(hù)數(shù)比1990年時(shí)增加了大約60倍,平均每位用戶(hù)每天使用手機(jī)的時(shí)間也達(dá)到20分鐘,而在通訊費(fèi)用昂貴的早期,這一數(shù)字還僅為一到兩分鐘。隨著用戶(hù)相互之間的通話(huà)時(shí)間越來(lái)越長(zhǎng),通話(huà)總時(shí)長(zhǎng)也在迅速水漲船高。

????以下圖表綜合了來(lái)自美國(guó)國(guó)家癌癥研究院和手機(jī)行業(yè)主要行業(yè)協(xié)會(huì)的數(shù)據(jù),看起來(lái)頗為有趣。

????During the 1980s, just as Americans began pumping low-frequency radiation through their skulls with cell phones, brain cancer rates in the U.S. slowly increased. At the beginning of the decade, doctors delivered the devastating diagnosis of brain cancer to 63 out of every 1 million Americans every year; by 1990 that number had risen to 70 per million. And that's when cell phone usage really took off.

????Yet while the link between phones and tumors may have seemed certain to grow, a strange thing happened. Beginning in 1991 the rate of brain cancer incidence reversed course and began to slowly fall. By 2008, the last year for which the National Cancer Institute has data, 65 out of every 1 million Americans got a brain cancer diagnosis annually.

????During those same two decades, the radiation beamed by phones into American brains increased about 500-fold, in proportion to the wild growth in cell phone use. There are roughly 60 times more cell phones in the U.S. than there were in 1990, and each one is used for an average of about 20 minutes per day, up from just a minute or two in the industry's expensive early days. The combined effect of more customers each talking more has been a stunning increase in total talk time.

????Combining data from the National Cancer Institute and the cellular industry's main trade group yields this intriguing graph:

????布朗大學(xué)(Brown University)的傳染病科教授戴維?薩維茨曾進(jìn)行過(guò)這類(lèi)研究,他警告說(shuō),雖然從圖中能很清晰地看到手機(jī)輻射量與腦癌發(fā)病率之間沒(méi)有關(guān)系,但并不能完全證明手機(jī)是安全的。最令人擔(dān)憂(yōu)的是,使用手機(jī)和最終罹患腦癌之間可能存在漫長(zhǎng)的時(shí)間間隔。

????不過(guò)塞維茨同時(shí)也認(rèn)為,(低頻)輻射量大幅增加不會(huì)導(dǎo)致腦癌患者總?cè)藬?shù)上升這一發(fā)現(xiàn)是令人信服的。即便輻射暴露與罹患腦癌之間的平均時(shí)間間隔長(zhǎng)達(dá)30年,但現(xiàn)實(shí)中必然會(huì)有在20年后就患病的特例者,這些人肯定會(huì)體現(xiàn)在目前的數(shù)據(jù)中。(情形與人們?cè)缙谑艿绞薜任镔|(zhì)輻射,很長(zhǎng)時(shí)間后才出現(xiàn)癥狀;類(lèi)似。)雖然1990年時(shí)的手機(jī)用戶(hù)總數(shù)非常低,但也有足足500萬(wàn)人。在2008年時(shí)哪怕這些早期使用者中只有很少一部分人染上因手機(jī)輻射導(dǎo)致的腦癌,那么當(dāng)年的腦癌發(fā)病率也會(huì)出現(xiàn)大幅上升。

????曾擔(dān)任過(guò)《美國(guó)流行病學(xué)雜志》(American Journal of Epidemiology)編輯一職的薩維茨表示:“真正的問(wèn)題是,病情什么時(shí)候開(kāi)始爆發(fā)?假如沒(méi)有跡象表明問(wèn)題是何時(shí)開(kāi)始發(fā)生的,那么相對(duì)于其它我們研究過(guò)的誘因,這次的情況可能將是史無(wú)前例的?!?/p>

????上周,世界衛(wèi)生組織(World Health Organization)發(fā)布了一項(xiàng)研究報(bào)告,認(rèn)定手機(jī)“可能致癌”,此結(jié)論主要基于一項(xiàng)研究發(fā)現(xiàn):重度手機(jī)用戶(hù)罹患神經(jīng)膠質(zhì)瘤的風(fēng)險(xiǎn)增加了40%。據(jù)報(bào)道,這些用戶(hù)在10年里平均每天使用手機(jī)通話(huà)的時(shí)間超過(guò)30分鐘。對(duì)于典型的美國(guó)電話(huà)電報(bào)公司用戶(hù)(AT&T)而言,這個(gè)消息有點(diǎn)可怕。今年第一季度,他們的平均每天通話(huà)時(shí)間達(dá)到了21分鐘。而對(duì)于MetroPCS和Leap Wireless的用戶(hù)來(lái)說(shuō),這個(gè)消息簡(jiǎn)直就是個(gè)噩耗。MetroPCS和Leap Wireless是專(zhuān)門(mén)從事替代固話(huà)服務(wù)的等廉價(jià)服務(wù)商。目前,Leap的語(yǔ)音用戶(hù)平均每天通話(huà)時(shí)間已經(jīng)達(dá)到了驚人的50分鐘。

????不過(guò),至少到目前為止,所有重度用戶(hù)腦癌的整體發(fā)病率并沒(méi)有上升。

????手機(jī)到底會(huì)不會(huì)導(dǎo)致腦癌?要得到這個(gè)問(wèn)題的最終答案,我們還得等上幾十年時(shí)間,等到人們所接受的輻射量真正穩(wěn)定在高水平,而腦癌發(fā)病率的趨勢(shì)出現(xiàn)明顯變化,要么掉頭上升,要么繼續(xù)下降。目前,輻射量已經(jīng)開(kāi)始趨于穩(wěn)定。在經(jīng)歷了30多年的高速發(fā)展后,美國(guó)用戶(hù)的手機(jī)通話(huà)時(shí)長(zhǎng)在2010年時(shí)已經(jīng)穩(wěn)定在了每年2.7萬(wàn)億分鐘的水平上。

????譯者:項(xiàng)航

????The chart's clear disconnect between radiation dose and cancer rates does not conclusively prove cell phone are safe, cautions David Savitz, a Brown University epidemiology professor who has studied the issue. Most worrisome, it's possible there is simply a huge delay between a person using a cell phone and that exposure causing a brain tumor.

????Yet Savitz also finds the utter lack of an increase in total brain cancer following the massive increase in (low-level) radiation very reassuring. Even if the average lag between exposure and symptoms was 30 years, there would almost certainly be outliers who develop symptoms after just 20 years -- outliers who would be showing up in the data by now. (That's what's happened after early exposures to things like asbestos.) Total cell phone use may have been far lower in 1990, but there were already 5 million subscribers. It wouldn't take many of those early adopters coming down with cell phone-caused brain cancer to bump up the cancer rates in 2008.

????"The real question is: When would we see the beginning of the epidemic?" says Savitz, the former editor of the American Journal of Epidemiology. "It would be unprecedented relative to other agents we've studied to have no evidence of the beginning of the problem."

????The World Health Organization study released last week classified cell phones as "possibly carcinogenic to humans," based largely on a study that found a 40% increased risk for a cancer called gliomas among heavy cell phone users. Those users reported averaging 30 minutes per day talking on their phones over a 10‐year period. That's somewhat scary news for the typical AT&T (T) customer, who averaged 21 minutes a day in the first quarter of this year. And it's really scary for customers of low-cost providers that specialize in replacing landline service such as MetroPCS (PCS) or Leap Wireless (LEAP). Customers of Leap's Cricket service average a whopping 50 minutes per day.

????And yet, so far at least, all that talking hasn't jacked up the overall incidence of brain cancer.

????The ultimate answer to the question of whether cell phones cause brain cancer will only be definitively resolved after a few more decades in which the population's radiation dose stabilizes at a high level and brain cancer rates either jump or continue to decline. That stabilizing has already happened. After three decades of stunning growth, time spent talking on cell phones in the U.S. leveled off in 2010 at 2.7 trillion minutes a year.

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