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."

    在不久將來潛在型毒害神經的阻燃劑將從市場上蕩出，它會漫漫在我們的食物鏈消失。

    至今人類暴露于溴化阻燃劑，或多溴聯苯醚的最為廣泛的分析之一給出，化學品長期應用于上至電腦，下至睡袋-從人類涉取的食物中進入人體，不僅僅限制于自己的家人。

    "你吃的東西越多，就有越多的PBDES存在于你的血漿中，"在波士頓大學公共健康學的環境健康學者Alicia Fraser--一項新研究（這項研究被發表在這個月的環境健康透視期刊上）的發起人指出。

    PBDES是多氯化聯苯，或多氯聯苯衍生物的化學生成物（同類物質）,它們能夠導致出生缺陷和神經損害。多氯聯苯衍生物從70年代中葉就已經被全世界所禁止使用，那時也正是PBDES以阻燃劑的名義而普遍受到歡迎的時候。PBDES很快就被發現是家庭用品中很有塑料制品最多的物質。

    直到90年代后期，使用PBDES的數量在全球范圍內成為普及，在美國的發現使用量是最多的。研究者們就緊張起來：在動物實驗中，低計量食用能導致神經受損，然而更高人類涉入PBDE量還是從母乳中獲得的。

    至于是否PBDES對人類來說是場危機還不感肯定。直接測試是不合乎常規的，對于人類普遍流行病學研究是很難運行的。但是我們有足夠的理由去為在2004年歐洲聯盟禁止大約2/3的PBDE劑型使用而擔憂。

    環境保護局在一月承認，他們缺乏確立對化學品安全的的基本標準的能力，沒有依照按例，但是三個國家-加洲，華盛頓和緬因州已經從2007年就禁止了PBEDS的使用。許多生產廠商們也已經停止和在計劃不使用PBEDS.

    "它們會不斷在環境中蔓延。它們不會被終止。因為它們作為污染物滯留在環境和我們身體中真的已經有很長一段歷史了，"Fraser說道。即使我們不知道在這一點上它對我們健康的影響狀況，大多數人們還是需要有相應的政策來抵制我們在接觸到它。"

    但是雖然我們一在的提倡，這些指令也不會降低它帶來的危險。大多數對PBDE暴露的研究還是聚焦于人類如何能夠從灰塵和其它室內資源中吸收它，這樣就能將它從表面上去除，一旦發現PBDE含在產品中，就將它除掉。很少有人關心PBDES是否在食物中含有。

    Fraser的小組從2000個人中分析他們的生物樣品，樣品是由美國疾病控制和保護中心提供的。相同的數據被應用于2004年美國建立PBDE暴露的基礎評估，但是那項研究并沒有找出它存在于食物消耗中的模式。Fraser的小組發現PBDE含量蔬菜素食者比在肉類食用者中低了25%.

    雖然食物被PBDE污染的渠道并沒有最后被確立，"老產品"要被采取垃圾掩埋法是可能的，PBDES可以從這個辦法中進入環境，"Fraser說。在前幾年，國家海洋和大氣管理局宣告PBDES存在于所有美國近海和北美洲五大湖中，在城市和工業地區被發現的含量尤為高。

    PBDES（作為存在于脂肪里的化學品堆積者）將會是肉類產品中含量最多的，這是可以想象的，所以對于PBDES來說想要進入它們喂養和水中沒有那么困難。

    Fraser建議美國采用化學調節的這個辦法與歐洲聯盟是一樣的，他們在2007年委托統治了，化學品必須完全要通過試驗，被證實安全后才能使用。那正好跟美國系統的做法相反。在那，化學品都認為它是安全，除非你有證據證實它不安全。

    "工業正在尋找一種新產品來用它作阻燃劑使用，我們不清楚那些產品的健康跟安全指示，"Fraser說。"我們需要在產品投入使用之前檢測產品的健康和安全指示，而不是之后。"