The warnings we must listen to Clive Cookson
Any new technology introduced rapidly into the consumer market arouses safety fears and these can be very hard to dispel. When the Victorians worried about the “force fields” associated with new-fangled electric power, scientists could not provide absolute reassurance and even today there are unresolved concerns about the health risks from power lines.
The introduction of mobile phones in the early 1980s was accompanied by allegations that the microwave radiation used to transmit conversations between base stations and handsets could cause brain damage leading to memory loss and malignant tumours. After hundreds of studies around the world, the evidence remains inconclusive today.
So when Sir William Stewart, chairman of the UK's National Radiological Protection Board, issued an update last week on his landmark 2000 review of mobile phone safety, the conclusion was virtually the same as five years ago. “There is no hard evidence at present that the health of the public in general is being affected adversely by the use of mobile phone technologies,” he said, “but uncertainties remain and a continued precautionary approach to their use is recommended.” He has, for instance, discouraged the use of mobile phones by his grandchildren.
Several individual studies have shown harmful effects from mobile phones. But Anthony Swerdlow of the Institute of Cancer Research in London, who chairs the UK Advisory Group on Non-Ionising Radiation, is wary of these findings. “These one-off positives have not been replicated on a more substantial scale,” he says, “so we cannot know whether they were the result of a statistical coincidence.”
The most recent report and for many experts the most troubling was published last October by scientists at the Karolinska Institute in Sweden. This study showed that people who used mobile phones for more than 10 years had a doubled risk of developing acoustic neuroma, a slow-growing tumour of the nerve between the ear and brain. Although a benign tumour, it leads to deafness and loss of balance and, if it is not removed surgically, it will eventually kill the patient. The most striking finding of the study, which included 150 acoustic neuroma patients and 600 healthy controls, was that the increased risk was confined to the side of the head where the phone was normally held. “It is a strong association,” says Anders Ahlbom, the research director, “but in science, even when you have a strong association, the results need to be replicated before you can draw any firm conclusions.”
Confirmation or otherwise may occur later this year. The Swedish study is part of a large collaboration called Interphone, which is co-ordinated by the International Agency for Research on Cancer (IARC) in the southern French city of Lyon. This involves researchers from 13 countries using similar methodology to investigate three types of tumour whose location makes them the most likely candidates for a link with mobile phone radiation.
Altogether, they are studying 6,000 people with brain tumours: 1,000 with acoustic neuromas and 600 with tumours of the salivary gland together with matched controls. The details of mobile-phone use is obtained by interview, and validated by phone company records.
So far, the only other national Interphone study to have reported results is Denmark's, which found no link with acoustic neuroma but it is smaller than the Swedish study and includes fewer long-term users. Elisabeth Cardis, Interphone leader at the IARC, says that more national studies will be published during 2005 and early results from the international programme should be available this year too.
Interphone, the world's largest project looking at mobile phone epidemiology (health effects among users), is funded by industry and governments. Dr Cardis says the mobile phone manufacturers have contributed �3.5m, the European Commission �3.85m and national sources at least �3m more.
“It is the responsibility of the industry to support research into mobile phone safety, but its contributions must go through an effective ‘firewall' in order to maintain scientific impartiality,” Prof Ahlbom says. “Interphone has a double firewall: the money goes first to the International Union Against Cancer and then to IARC.” In the UK, the government and the industry have contributed to the ￡8.8m Mobile Telecommunications Health Research programme run by an independent committee of senior academic scientists. This has funded 28 individual projects, most of which are still in progress.
The research falls into two broad categories. One looks for the effects of mobile phones on people, through epidemiological studies and tests on volunteers for example, to see if the radiation affects their brain function. The other approach exposes laboratory animals or cell cultures to radiation simulating mobile phone emissions: this allows scientists to investigate longer or more intense exposures than they could with humans.
Lab studies, like epidemiological research, have given some worrying results but there is no sustained evidence of harm. For example, while a study of rats exposed to phone radiation undertaken by scientists at Lund University in Sweden found significant brain damage, a similar study at Washington University in St Louis found no ill effects.
Most of the scientists say that the industry has so far given a reasonable level of support for research into mobile phone safety: its total expenditure worldwide runs to tens of millions of dollars, though an exact figure is not available. But Prof Ahlbom says he and his colleagues worry that companies are holding back on commitments to fund future work.
The main weakness of the existing research is that virtually no work has been done on the impact on children. Yet a child is more likely than an adult to be vulnerable to any harmful effects because its skull is thinner, its nervous system is still developing and it potentially has a lifetime of exposure. “We are thinking of proposing to the World Health Organisation that we do a feasibility study for a kids' version of the Interphone programme,” says Dr Cardis of IARC. “If Interphone shows adverse effects among adults, we can follow up looking at young people and adolescents.”
Another proposal, for which a feasibility study has been carried out, is to conduct a long-term international “cohort study”. Prof Ahlbom says this would follow as many as 250,000 young people, relating their state of health to the way they use mobile phones.
As time passes, manufacturers are progressively reducing the power output of their phones, so radiation risks to individual users are diminishing. However, as the number of subscribers surges past 1.5bn, even a tiny individual health risk could translate into thousands of deaths. The safety of mobile phones is sure to remain a contentious issue for many years to come.
Part II on Monday: How the industry is managing the scare
我们必须接听的手机警报
任何迅速引入消费市场的新技术都会引发安全问题上的担忧，而且很难消除。维多利亚女王时代，当人们对新发明的电力产生的“力场”感到担心时，科学家无法让他们绝对放心。即使时至今日，对于电力线健康风险的担心尚未消除。
80年代初，随着手机的出现，各种罪名也随之而来。用于传输基点和手机间通话的微波辐射可能会造成大脑损伤，并导致失忆和恶性肿瘤。在全世界进行了数百份研究后，手机辐射尚未盖棺定论。
所以，当英国国家放射防护局局长威廉?斯图尔特爵士(Sir William Stewart)上周公布了具有深远意义的手机安全2000回顾时，结论实际上与5年前相同。“现在，缺乏确凿的证据证明，使用手机技术会对普通公众的健康造成不利的影响，”他说，“但各种不确定依然存在，而且对于使用手机继续采取一种防患于未然的态度是值得推荐的。”例如，他不赞成孙子（女）使用手机。
几份个别的研究已证明了手机的危害。但是，来自伦敦癌症研究院的安东尼?斯沃德罗(Anthony Swerdlow)，同时也是英国非电离辐射咨询委员会主席，对于这些发现结果显得小心谨慎。“这些证明手机辐射有害的证据还没有在一个更大的规模上进行反复验证，“所以，我们无法知道它们是否是统计巧合的结果。”
去年10月，瑞典卡洛林斯卡医学院的科学家公布了最新的一份报告，这也是最令许多专家烦恼的报告。该研究显示，使用手机10年以上的人罹患听神经瘤的风险是不使用手机的人的两倍。听神经瘤是一种耳脑之间发展缓慢的神经瘤。虽然这是一种良性肿瘤，但会导致耳聋和失去平衡。而且，如果不能通过手术去除的话，它将最终夺去病人的生命。该研究涉及150名听神经瘤病人和600个健康控制中心，其中最显著的发现是，患病风险的增加局限于通常手持电话的那边大脑。“这是一种密切的关联，”研究主任安德思?阿尔博恩(Anders Ahlborn)说，“但在科学界，即使你掌握了很强的关联，在做出任何肯定的结论前，你必须对结果进行反复论证。”
今年晚些时候，可能会得到手机对人体危害的证明或反证。瑞典医学院的研究结果是名为Interphone庞大合作机构的一部分，由国际癌症研究署(IARC，在法国里昂)进行协调。Interphone涉及来自13个国家的研究人员，使用相似的方法研究3类肿瘤，这些肿瘤生长的位置与手机辐射最有关系。
他们正在研究总共6000名的脑瘤患者，其中1000人患有听神经瘤，600人患有唾腺瘤以及。科学家通过与患者交谈，获取手机使用的详情，并通过手机公司的记录进行确认。
到目前为止，除瑞典外，丹麦是唯一一个报告Interphone研究结果的国家，它发现手机与听神经瘤之间没有关系。但该国研究规模比瑞典研究小，而且包含的手机长期使用者较少。IARC中Interphone的负责人伊丽莎白?卡迪斯(Elisabeth Cardis)说，2005年公布的国家研究将会更多，而且今年也将获得来自国际课题的早期结果。”
研究手机流行病学（使用者中的健康效应）的全球最大项目Interphone获得了行业和政府的资助。卡迪斯医生说，手机制造商和欧洲委员会已分别捐资350万欧元和385万欧元，获得的国家资源至少在300万欧元以上。
“资助手机安全的研究是行业的职责所在，但其捐资必须经过一个有效的“防火墙”，从而保持科学的公正性，”阿尔博恩博士说，“Interphone拥有一个双重防火墙，即资金首先进入国际抗癌联盟，然后到达IARC。”在英国，政府和行业已对手机通信健康研究计划捐资880万欧元，该计划由一个由资深学术科学家组成的独立委员会进行运作。它已资助了28个独立项目，其中大部分仍在进行中。
该研究分为两大类。一类是寻找手机对人体的影响，采用的方式是流行病学研究，并对志愿者进行测试，观察辐射是否会影响他们大脑功能。另外一种方式是使实验室中的动物或细胞培养暴露在模拟手机发出的辐射中。这使科学家研究的时间更长，研究的辐射强度也比人体更大。
和流行病学一样，实验室研究已提供了一些令人担心的结果，但没有持续证据来表明手机对人体有害。例如，虽然瑞典隆德大学(Lund University)的科学家对于暴露在手机辐射中的老鼠进行研究，发现手机辐射对大脑具有重大危害，但圣路易斯的华盛顿大学进行的一份相似的研究没有发现任何危害。
大多数科学家表示，迄今为止，行业已对手机安全的研究给予了适度的支持。虽然缺乏精确的数字，但全球总支出达数千万美元。但阿尔博恩教授说，他和他的同事担心，公司对于资助未来工作的承诺裹足不前。
现有研究的主要缺点是实际上尚未针对手机对儿童的影响进行研究。但儿童比成人更容易遭受任何伤害，因为它的头骨更薄，神经系统还在发育，而且它受到手机辐射的影响可能是一生的。“我们正在考虑向世界卫生组织(WHO)提议，为Interphone计划的儿童版进行可行性研究，”IARC的卡迪斯医生说，“如果Interphone显示的是，手机对成人不利的影响，那么我们可以继续研究它对年轻人和青少年的影响。”
另外一份可行性研究已经完成的计划书将进行长期的国际“定群研究”。阿尔博恩博士说，该研究将追踪多达25万年轻人，将其健康状态与使用手机的方式联系起来。
随着时间的推移，制造商正在逐步减少手机的功率输出，所以辐射对于使用者的风险正在减少。然而，随着手机用户数量突破15亿，即使是一个很小的个人健康风险也有可能转变为数以千计的死亡。在未来的许多年中，手机的安全问题必将仍是一个具有争议的问题。
