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(lái)潛在型毒害神經(jīng)的阻燃劑將從市場(chǎng)上蕩出，它會(huì)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(lián)苯醚的最為廣泛的分析之一給出，化學(xué)品長(zhǎng)期應(yīng)用于上至電腦，下至睡袋-從人類涉取的食物中進(jìn)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(xué)公共健康學(xué)的環(huán)境健康學(xué)者Alicia Fraser--一項(xiàng)新研究（這項(xiàng)研究被發(fā)表在這個(gè)月的環(huán)境健康透視期刊上）的發(fā)起人指出。

    PBDES是多氯化聯(lián)苯，或多氯聯(lián)苯衍生物的化學(xué)生成物（同類物質(zhì)）,它們能夠?qū)е鲁錾�缺陷和神�?jīng)損害。多氯聯(lián)苯衍生物從70年代中葉就已經(jīng)被全世界所禁止使用，那時(shí)也正是PBDES以阻燃劑的名義而普遍受到歡迎的時(shí)候。PBDES很快就被發(fā)現(xiàn)是家庭用品中很有塑料制品最多的物質(zhì)。

    直到90年代后期，使用PBDES的數(shù)量在全球范圍內(nèi)成為普及，在美國(guó)的發(fā)現(xiàn)使用量是最多的。研究者們就緊張起來(lái)：在動(dòng)物實(shí)驗(yàn)中，低計(jì)量食用能導(dǎo)致神經(jīng)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(duì)人類來(lái)說(shuō)是場(chǎng)危機(jī)還不感肯定。直接測(cè)試是不合乎常規(guī)的，對(duì)于人類普遍流行病學(xué)研究是很難運(yùn)行的。但是我們有足夠的理由去為在2004年歐洲聯(lián)盟禁止大約2/3的PBDE劑型使用而擔(dān)憂。

    環(huán)境保護(hù)局在一月承認(rèn)，他們?nèi)狈Υ_立對(duì)化學(xué)品安全的的基本標(biāo)準(zhǔn)的能力，沒(méi)有依照按例，但是三個(gè)國(guó)家-加洲，華盛頓和緬因州已經(jīng)從2007年就禁止了PBEDS的使用。許多生產(chǎn)廠商們也已經(jīng)停止和在計(jì)劃不使用PBEDS.

    "它們會(huì)不斷在環(huán)境中蔓延。它們不會(huì)被終止。因?yàn)樗鼈冏鳛槲廴疚餃�留在環(huán)境和我們身體中真的已經(jīng)有很長(zhǎng)一段歷史了，"Fraser說(shuō)道。即使我們不知道在這一點(diǎn)上它對(duì)我們健康的影響狀況，大多數(shù)人們還是需要有相應(yīng)的政策來(lái)抵制我們?cè)诮佑|到它。"

    但是雖然我們一在的提倡，這些指令也不會(huì)降低它帶來(lái)的危險(xiǎn)。大多數(shù)對(duì)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(nèi)資源中吸收它，這樣就能將它從表面上去除，一旦發(fā)現(xiàn)PBDE含在產(chǎn)品中，就將它除掉。很少有人關(guān)心PBDES是否在食物中含有。

    Fraser的小組從2000個(gè)人中分析他們的生物樣品，樣品是由美國(guó)疾病控制和保護(hù)中心提供的。相同的數(shù)據(jù)被應(yīng)用于2004年美國(guó)建立PBDE暴露的基礎(chǔ)評(píng)估，但是那項(xiàng)研究并沒(méi)有找出它存在于食物消耗中的模式。Fraser的小組發(fā)現(xiàn)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(méi)有最后被確立，"老產(chǎn)品"要被采取垃圾掩埋法是可能的，PBDES可以從這個(gè)辦法中進(jìn)入環(huán)境，"Fraser說(shuō)。在前幾年，國(guó)家海洋和大氣管理局宣告PBDES存在于所有美國(guó)近海和北美洲五大湖中，在城市和工業(yè)地區(qū)被發(fā)現(xiàn)的含量尤為高。

    PBDES（作為存在于脂肪里的化學(xué)品堆積者）將會(huì)是肉類產(chǎn)品中含量最多的，這是可以想象的，所以對(duì)于PBDES來(lái)說(shuō)想要進(jìn)入它們喂養(yǎng)和水中沒(méi)有那么困難。

    Fraser建議美國(guó)采用化學(xué)調(diào)節(jié)的這個(gè)辦法與歐洲聯(lián)盟是一樣的，他們?cè)?007年委托統(tǒng)治了，化學(xué)品必須完全要通過(guò)試驗(yàn)，被證實(shí)安全后才能使用。那正好跟美國(guó)系統(tǒng)的做法相反。在那，化學(xué)品都認(rèn)為它是安全，除非你有證據(jù)證實(shí)它不安全。

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