Long after a potentially neurotoxic flame retardant is off the market, it could linger in our food chain.

One of the most comprehensive analyses yet of human exposure to PBDEs, or polybrominated diphenyl ethers, shows that the chemical - long used in everything from computers to sleeping bags - enters humans through their diets, not just their household.

"The more you eat, the more PBDEs you have in your serum," said Alicia Fraser, an environmental health researcher at Boston University's School of Public Health who headed the new study, published this month in Environmental Health Perspectives.

PBDEs are chemical cousins of polychlorinated biphenyls, or PCBs, which are known to cause birth defects and neurological impairments. PCBs were banned throughout the world by the mid-1970s, when PBDEs were gaining popularity as flame retardants. PBDEs were soon found in most plastic-containing household products.

By the late 1990s, trace amounts of PBDEs had been found in people all over the world, with the highest exposures measured in the United States. Researchers became nervous: Low doses caused neurological damage in laboratory animals, and the highest human PBDE levels were found in breast milk.

Whether PBDEs posed an immediate threat to humans was uncertain. Direct testing is unethical, and population-wide epidemiological studies are difficult to run. But there's enough reason for concern that the European Union banned two of the three most common PBDE formulations in 2004.

The Environmental Protection Agency, which in January admitted that it lacked the ability to establish basic standards of chemical safety, has not followed suit, but three states - California, Washington and Maine - have banned PBDEs since 2007. Many manufacturers have either stopped or plan on stopping their use.

"They are persistent in the environment. They don't get broken down. Therefore, it takes a really long time for the contamination to leave our environment and our bodies," said Fraser. "Even though we don't know the health effects at this point, most people would want policies that would stop us from being exposed to them."

But though well-advised, these bans won't eliminate the threat. Most PBDE exposure research has focused on how people can absorb it from dust and other indoor sources that would ostensibly be eliminated once PBDE-containing products were discarded. Much less attention has been paid to PBDEs in food.

Fraser's team analyzed biological samples from 2,000 people, provided by the U.S. Centers for Disease Control and Prevention. The same data was used in 2004 to establish baseline estimates of PBDE exposure in Americans, but that study didn't look for patterns in food consumption. Fraser's team found that PBDE levels were 25 percent higher in meat-eaters than vegetarians.

Though the channels of food contamination by PBDEs haven't been conclusively established, it's possible that "the old products are being moved to landfills, and PBDEs could enter the environment that way," said Fraser. Earlier this year, the National Oceanic and Atmospheric Administration announced that PBDEs were present in all U.S. coastal waters and the Great Lakes, with the highest levels found near urban and industrial areas.

That PBDEs would be highest in meat products makes sense, as the chemicals accumulate in fat, and it wouldn't be hard for PBDEs to enter their feed and water.

Fraser suggested that the United States adopt chemical regulations similar to those in the European Union, which in 2007 mandated that chemicals be thoroughly tested and proven safe before used. That's the opposite of the U.S. system, where chemicals are assumed to be safe until it's proved otherwise.

"The industry is finding new products to use as flame retardants, and we don't know the health and safety implications of those products either," said Fraser. "We need to test the health and safety implications of products before they go into use, not after."

在不久将来潜在型毒害神经的阻燃剂将从市场上荡出，它会漫漫在我们的食物链消失。

至今人类暴露于溴化阻燃剂，或多溴联苯醚的最为广泛的分析之一给出，化学品长期应用于上至电脑，下至睡袋-从人类涉取的食物中进入人体，不仅仅限制于自己的家人。

"你吃的东西越多，就有越多的PBDES存在于你的血浆中，"在波士顿大学公共健康学的环境健康学者Alicia Fraser--一项新研究（这项研究被发表在这个月的环境健康透视期刊上）的发起人指出。

PBDES是多氯化联苯，或多氯联苯衍生物的化学生成物（同类物质）,它们能够导致出生缺陷和神经损害。多氯联苯衍生物从70年代中叶就已经被全世界所禁止使用，那时也正是PBDES以阻燃剂的名义而普遍受到欢迎的时候。PBDES很快就被发现是家庭用品中很有塑料制品最多的物质。

直到90年代后期，使用PBDES的数量在全球范围内成为普及，在美国的发现使用量是最多的。研究者们就紧张起来：在动物实验中，低计量食用能导致神经受损，然而更高人类涉入PBDE量还是从母乳中获得的。

至于是否PBDES对人类来说是场危机还不感肯定。直接测试是不合乎常规的，对于人类普遍流行病学研究是很难运行的。但是我们有足够的理由去为在2004年欧洲联盟禁止大约2/3的PBDE剂型使用而担忧。

环境保护局在一月承认，他们缺乏确立对化学品安全的的基本标准的能力，没有依照按例，但是三个国家-加洲，华盛顿和缅因州已经从2007年就禁止了PBEDS的使用。许多生产厂商们也已经停止和在计划不使用PBEDS.

"它们会不断在环境中蔓延。它们不会被终止。因为它们作为污染物滞留在环境和我们身体中真的已经有很长一段历史了，"Fraser说道。即使我们不知道在这一点上它对我们健康的影响状况，大多数人们还是需要有相应的政策来抵制我们在接触到它。"

但是虽然我们一在的提倡，这些指令也不会降低它带来的危险。大多数对PBDE暴露的研究还是聚焦于人类如何能够从灰尘和其它室内资源中吸收它，这样就能将它从表面上去除，一旦发现PBDE含在产品中，就将它除掉。很少有人关心PBDES是否在食物中含有。

Fraser的小组从2000个人中分析他们的生物样品，样品是由美国疾病控制和保护中心提供的。相同的数据被应用于2004年美国建立PBDE暴露的基础评估，但是那项研究并没有找出它存在于食物消耗中的模式。Fraser的小组发现PBDE含量蔬菜素食者比在肉类食用者中低了25%.

虽然食物被PBDE污染的渠道并没有最后被确立，"老产品"要被采取垃圾掩埋法是可能的，PBDES可以从这个办法中进入环境，"Fraser说。在前几年，国家海洋和大气管理局宣告PBDES存在于所有美国近海和北美洲五大湖中，在城市和工业地区被发现的含量尤为高。

PBDES（作为存在于脂肪里的化学品堆积者）将会是肉类产品中含量最多的，这是可以想象的，所以对于PBDES来说想要进入它们喂养和水中没有那么困难。

Fraser建议美国采用化学调节的这个办法与欧洲联盟是一样的，他们在2007年委托统治了，化学品必须完全要通过试验，被证实安全后才能使用。那正好跟美国系统的做法相反。在那，化学品都认为它是安全，除非你有证据证实它不安全。

"工业正在寻找一种新产品来用它作阻燃剂使用，我们不清楚那些产品的健康跟安全指示，"Fraser说。"我们需要在产品投入使用之前检测产品的健康和安全指示，而不是之后。"