Some puzzling studies appear to show that tiny airborne particles may contribute to obesity, diabetes and heart disease. Should we be concerned?
一些令人困惑的研究表明空气中的微小悬浮颗粒可导致肥胖、糖尿病和心脏病。是否应该引起我们的关注？
Take a deep breath, and exhale. Depending on where you live, that life-giving lungful of air might just be pushing you towards diabetes and obesity.
由于生存环境的不同，维持生命的呼吸可能会使你患上糖尿病或者肥胖。
The idea that “thin air” can make you fat sounds ludicrous, yet some extremely puzzling studies appear to be showing that it’s possible. Two people can eat the same foods, and do the same exercise, but over the course of a few years, one may put on more weight and develop a faulty metabolism – thanks to the atmosphere around their home.
“虚无的空气”会导致肥胖的观点听起来有些荒唐，然而一些令人非常困惑的研究显示这是很有可能的。两个饮食和锻炼相同的人，几年后其中一个可能会出现肥胖和新陈代谢问题，这就是他们家周围的大气造成的。
Traffic fumes and cigarette smoke are the chief concerns, with their tiny, irritating particles that trigger widespread inflammation and disrupt the body’s ability to burn energy. While the short-term effects are minimal, over a lifetime it could be enough to contribute to serious disease – besides the respiratory illnesses more commonly associated with smog. “We are starting to understand that the uptake and circulation of air pollution in the body can affect more than just the lungs,” says Hong Chen at the University of Toronto, Canada.
首先要关注的是汽车尾气和香烟，微小的刺激性颗粒会引起大范围的炎症并扰乱身体燃烧能量的机制。虽然短期的影响很小，但在一生中除了会造成雾霾直接相关的呼吸道疾病之外，还会造成一些严重的疾病。加拿大多伦多大学的陈红说：“我们逐渐了解到体内吸入污染的空气还会造成肺部以外的影响。”
How strong is the evidence from these studies, and should you be concerned?
这些研究的证据是否可靠，你是否会关注？
Laboratory mice offered some of the earliest concrete clues that the effects of air pollution may penetrate far beyond the lungs. Their breeder at the Ohio State University, Qinghua Sun, had been interested in studying why city-dwellers seem to be at a particularly high risk of heart disease compared to country folk. Lifestyle, of course, could be one reason: in most major cities a fast food chain is rarely more than a block away, for instance, which might encourage unhealthy eating. Nevertheless, he wondered if another answer may be hanging, invisibly, in the air we breathe.
实验室小白鼠最先提供的证据表明空气污染的远远不止对肺部有影响。这些小白鼠的饲养员，俄亥俄州立大学的孙庆华对城市居民患心脏病的风险比农村高这方面的研究很感兴趣。当然，生活方式也是一个重要的原因，例如多数大城市的众多快餐连锁店也会导致不健康饮食。然而，他想弄清呼吸的空气中是否有其他的答案。
To find out more, he started to raise laboratory mice in the kinds of conditions you might find across various cities. Some breathed filtered, clean, air, while others were funnelled the kinds of fumes you might find next to a motorway or busy city centre. Along the way, his team weighed the mice and performed various tests to study how their metabolism was functioning.
为了找到更多的证据，他开始在实验室里以不同城市的环境下饲养小白鼠。一些小白鼠呼吸过滤的干净空气，而另一些呼吸公路上或者繁忙市中心的污染空气。他们的团队在整个过程中对小白鼠称重和进行各种不同的测试，来研究小白鼠的新陈代谢是否正常。
After just 10 weeks, the effects were already visible. The mice exposed to the air pollution showed greater volumes of body fat, both around the belly and around the internal organs; at the microscopic level, the fat cells themselves were around 20% larger in the mice inhaling a fine mist of pollutants. What’s more, they seemed to have become less sensitive to insulin, the hormone that signals to cells to convert blood sugar into energy: the first step towards diabetes.
10周后影响就非常明显，呼吸污染空气的小白鼠体内脂肪，包括腹部脂肪和内部器官上的脂肪都比呼吸干净空气的小白鼠多。通过显微镜观察，呼吸污染空气的小白鼠的脂肪细胞要大20%。而且，看起来对胰岛素更加不敏感，这是糖尿病发展的第一步，胰岛素是一种向细胞发送信号把血糖转化为能量的激素。
The exact mechanism is still debated, but subsequent animal experiments suggest the air pollution triggers a cascade of reactions in the body. Small particles, less than 2.5 micrometres wide, are thought to be primarily to blame – the same minuscule motes of pollutant that give city air its gauzy haze. When we breathe in, the pollutants irritate the tiny, moist air sacs that normally allow the oxygen to pass into the blood stream. As a result, the lungs’ lining mounts a stress response, sending our nervous system into overdrive. This includes the release of hormones that reduce insulin’s potency and draws blood away from the insulin-sensitive muscle tissue, preventing the body from tightly controlling its blood sugar levels.
虽然准确机制还有待于讨论，但随后的实验表明空气污染造成了大量的体内反应。2.5微米以下的小颗粒可能是主要原因，这样的污染物小颗粒构成了城市里的雾霾。呼吸时这些污染物会刺激氧气交换的肺泡，肺部做出紧急响应，向神经系统发送紧张信号，包括释放降低胰岛素的荷尔蒙，减少胰岛素敏感肌肉组织的供血，影响了严格控制体内血糖水平。
The tiny irritating particles may also unleash a flood of inflammatory molecules called “cytokines” to wash through the blood, a response that also triggers immune cells to invade otherwise healthy tissue. Not only does that too interfere with the tissue’s ability to respond to insulin; the subsequent inflammation may also interfere with the hormones and the brain processing that govern our appetite, says Michael Jerrett at the University of California, Berkeley.
伯克利加州大学的麦克杰瑞特说，微小的刺激颗粒也会造成向血液中释放细胞活素类炎症细胞，也是触发免疫细胞防止侵害监控组织的一种响应。这样不仅过度的干涉组织响应胰岛素的能力，随之而来的炎症也会影响荷尔蒙和大脑控制饥饿的能力。
If the link is proven, how concerned should we be? The scientists stress that the individual, short-term risk to any one person is relatively small, and certainly shouldn’t be used as an excuse for obesity by itself, without considering other aspects of your lifestyle. But given the sheer number of people living in cities with high pollution, over the long term the total number of casualties could be enormous. “Everyone is affected by pollution to some degree,” says Brook. “It’s continuous, involuntary exposure, across billions of people – so the overall impact becomes much greater.”
布鲁克认同需要全球采取措施的观点，例如巴黎和伦敦这样的发达国家大都市可能会控制污染。北美和欧洲的污染控制发展趋势良好，但是我们不能只唱赞歌，改善全世界人类的健康应该是重中之重。