A troubling new study has found that the number of chemicals capable of impairing child development worldwide is more than double what was previously believed， according to a new story by Time Magazine.

Back in 2006， researchers from the Harvard School of Public Health and the Icahn School of Medicine at Mount Sinai pinpointed five industrial chemicals that they linked to brain disorders such as autism， attention deficit hyperactivity disorder （ADHD）， reduced IQ， and more.

These chemicals were lead， methlymercury， polychlorinated biphenyls （a coolant fluid in motors）， arsenic （found naturally and also in pesticides）， and toluene （in paint thinner， nail polish， and more）.

In a review of their 2006 study， though， the same scientists have now discovered brain development in children could be negatively disrupted by another six chemicals. These chemicals are： chlorpyrifos， dichlorodiphenyltrichloroethane， fluoride， manganese， polybrominated diphenyl ethers， tetrachloroethylene.

Alarmingly， the researchers discovered that manganese and fluoride， both of which are present in drinking water， can lead to poorer performance in school， lower math scores， and increased hyperactivity. High levels of fluoride， in particular， are potentially capable of lowering a child's IQ by seven points.

Chlorpyrifos， meanwhile， is a common pesticide that is still used in public areas and in agriculture despite the fact that the Environmental Protection Agency banned it from residential areas in 2001. According to a report by CNN in 2012， even low levels of chlorpyrifos could result in disrupted brain development.

\"It's out there and we do not know what the longer term impact is of lower levels，\" Virginia Rauh， professor of Clinical Population and Family Health at Columbia University Mailman School of Public Health， told CNN. \"But it does seem to be associated with cognitive damage and structural changes in brain.\"

As RT reported this week， some health experts believe the increased rate of severe birth defects in rural Washington state could possibly be linked to prolonged exposure to pesticides， though officials have been unable to determine the precise cause.

Despite the researchers’ claim that these new chemicals can contribute to brain disorders， they admitted they could not prove a direct causal link between a chemical and any one health issue. Still， they are pushing for increased public awareness considering the potential risks.

“The consequence of such brain damage is impaired [central nervous system] function that lasts a lifetime and might result in reduced intelligence， as expressed in terms of lost IQ points， or disruption in behavior，” the study reads， cited by Time and published in the Lancet Neurology journal.

時代雜志報道，一項最近研究發(fā)現(xiàn)，全世界造成兒童腦損傷的化學(xué)品比科學(xué)家估計的數(shù)量多一倍。2006年，哈佛大學(xué)公共健康學(xué)院及西奈的伊卡醫(yī)學(xué)院的科學(xué)家們指出了五種可能會造成自閉癥、多動癥和智商下降等腦疾病的工業(yè)化學(xué)品：鉛、甲基水銀、多氯聯(lián)苯（一種發(fā)動機冷卻劑）、砷（自然界及殺蟲劑中都有）和甲苯（涂料稀釋劑和指甲油中都有）。后來科學(xué)家們又發(fā)現(xiàn)了另外六種對兒童大腦發(fā)育產(chǎn)生負(fù)面影響的化學(xué)品：毒死蜱、滴滴涕、氟化物、錳、多溴聯(lián)苯醚、四氯乙烯。科學(xué)家還發(fā)現(xiàn)，飲用水中含有的錳和氟化物會導(dǎo)致學(xué)習(xí)成績下降、數(shù)學(xué)成績下降及多動。氟化物過多會導(dǎo)致智商下降7分。環(huán)境保護(hù)署自2001年就禁止了毒死蜱殺蟲劑的使用，但時至今日公共場所及農(nóng)業(yè)方面還在使用。哥倫比亞大學(xué)梅爾曼公共健康學(xué)院的弗吉尼亞·勞教授指出，盡管這些化學(xué)品與健康問題沒有確定的直接聯(lián)系，但它們造成的終身腦損傷會降低智力，或引起行為紊亂。

[http：//www.bbc.co.uk/news/health-26224812 ]