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  3. Drink from plastic bottles can raise the body’s levels of a controversial "gender-bending" chemical by more than two thirds, acc

Drink from plastic bottles can raise the body’s levels of a controversial "gender-bending" chemical by more than two thirds, acc

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问题     Drink from plastic bottles can raise the body’s levels of a controversial "gender-bending" chemical by more than two thirds, according to tests.
    Experts have been concerned about the possible health effects of bisphenol A(BPA)—an everyday chemical used in many plastic food and drink containers and tins as well as clear baby bottles—which is officially classified as toxic in some countries.
    A study found that participants who drank for a week from polycarbonate(聚碳酸酯)bottles showed a 69 percent increase in their urine(尿液)of BPA.
    Researchers did not say how much liquid was drunk per day. Researchers from Harvard School of Public Health studied 77 students, who had first undergone a seven-day "washout" phase in which they drank all cold beverages(饮料)from stainless steel bottles in order to minimise BPA exposure.
    They were then given two polycarbonate bottles and asked to drink all cold beverages from them during the next week. Previous studies have suggested that high levels of BPA consumption are linked to birth defects, growth problems and an increased risk of heart disease. In particular there are fears that heating the bottles, as parents would do when warming their baby’s milk, causes the chemical to leak in potentially dangerous quantities into the liquid contained within.
    "If you heat those bottles, as is the case with baby bottles, we would expect the levels to be considerably higher. This would be of concern since infants may be particularly susceptible to BPA’s hormone gland-disrupting(扰乱腺体激素分泌)potential. " said the senior author of the latest study, Karin B. Michels.
    Most adults carry BPA in their bodies but expert opinion on the risks is divided. The European Food Safety Authority believes that people naturally convert the chemical into less harmful substances in the body.
    Previous studies had found that BPA could leach(渗出)from polycarbonate bottles into their contents, but this study is the first to show the size of the corresponding increase in urinary BPA concentrations in humans.
    Harvard researcher Jenny Carwile said, " While previous studies have demonstrated that BPA is linked to adverse health effects, this study fills in a missing piece of the puzzle—whether or not polycarbonate plastic bottles are an important contributor to the amount of BPA in the body. "
According to Paragraph 4, the "washout" phase was designed to______.
选项 A、make the research be accomplished with a result as satisfactory as possible
B、obtain references for the possible health effects of stainless steel bottles
C、eliminate substances in bodies that may affect the result of the research
D、limit the sort of beverages taken in by participants to the minimum level
答案A
解析 推理判断题。由定位句可知，参加研究的被调查者首先要进行为期一周的“冲洗”，联系后文可知，在此之后的一周内被调查者还会被要求只用PC塑料瓶喝冰饮料。由此可推知，为期一周的“冲洗”是为了将两种情况进行对比，从而获得最好的研究效果，故A)为答案。让被调查者只能喝不锈钢瓶子装的冰饮料是为了让他们尽量不接触BPA，故排除B)；这里的“冲洗”只是一种形象的说法，并不指真的要将被调查者体内会影响研究结果的物质冲洗干净，故排除C)；“冲洗”阶段是为了将被调查者接触BPA的可能性最小化，而不是为了限制他们喝的饮料的种类，故排除D)。
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