在一項首次針對人類的同類型研究之中，研究人員發現備受爭議的化學物質雙酚A(BPA)可能與精子濃度與質量下降有關。
批評者認為，雙酚A會模仿人體本身的荷爾蒙，而對健康產生負面的影響。
雙酚A是製造食品包裝與飲料罐塑膠與環氧樹脂的常見原料，人們主要接觸的方式是透過飲食；皮膚的接觸，例如手持收銀機打字收據也是進入人體的途徑之一。
全球每年會生產超過60億磅的雙酚A。
研究報告的主要作者米克(John Meeker)，密西根大學公共衛生學院環境健康科學系助理教授說：「大部分雙酚A的研究都著重於在子宮內或是生命早期，這當然非常重要，不過本研究指出成年人暴露在雙芬A的風險也值得關注。」
「研究應著重於生命不同階段所受到的暴露風險」，米克說。
哈佛大學公共衛生學院生殖生理學教授豪澤爾(Russ Hauser)，在麻州總醫院與美國政府機構疾病控制與預防中心，與同事一同對本研究做出了貢獻。
這項研究發表在最近一期的「生殖毒理學」雜誌。
米克與豪澤爾在一個生育診所招募了190個人。在同一天取得了尿液與精子樣本。其中78人在之後的一個月又提供了一至兩個尿液樣本。
研究人員發現，89%的樣本內有雙酚A。
研究人員測量了精子濃度、活力、形狀和精子細胞DNA的損傷。
「比較受到高、低程度暴露的結果之後我們發現，暴露在高濃度雙酚A的男性，其精子濃度平均比低濃度的要少23%。」，米克說。
研究結果同時指出精子DNA損傷的狀況增加了10%。
先前的研究已經證明雙酚A對囓齒動物的精液有不良的影響，而這是首次有關雙酚A對人類精液影響的報導。
結果符合米克與豪澤爾先前的研究，某些荷爾蒙 - 促卵泡激素和抑制素B - 的升高或降低與雙酚A有關，此一模式符合精子數量的減少與發育遲緩。
由於本研究的設計以及相對較小的樣本數量，科學家說他們的結果只是「初步的，還需要進一步的研究。」
「研究數據的資料分析工作正在進行中」，豪澤爾說。「增加樣品數量並改善實驗設計之後，我們將能夠在不久的將來確認先前的研究結果。」
In one of the first human studies of its kind, researchers have found that urinary concentrations of the controversial chemical Bisphenol A, or BPA, may be related to decreased sperm quality and sperm concentration.
BPA mimics the body's own hormones and may lead to negative health effects, say critics of the chemical.
BPA is most commonly used to make plastics and epoxy resins used to line food and beverage cans, and people are exposed primarily through diet, although other routes are possible such as exposure through the skin when handling paper used to print cash register receipts.
Globally, more than six billion pounds of BPA are produced each year.
"Much of the focus for BPA is on the exposures in utero or in early life, which is of course extremely important, but this suggests exposure may also be a concern for adults," said the study's lead author, John Meeker, assistant professor of Environmental Health Sciences at the University of Michigan School of Public Health.
"Research should focus on impacts of exposure throughout multiple life stages," Meeker said.
Russ Hauser, a professor of reproductive physiology at Harvard School of Public Health, contributed to the research along with colleagues at Massachusetts General Hospital and the U.S. Centers for Disease Control and Prevention, a government agency.
The study is published in the current issue of the journal "Reproductive Toxicology."
Meeker and Hauser recruited 190 men through a fertility clinic. All gave spot urine samples and sperm samples the same day. Subsequently, 78 of the men gave one or two additional urine samples a month apart.
Researchers detected BPA in 89 percent of the urine samples.
Researchers measured sperm concentration, sperm motility, sperm shape and DNA damage in the sperm cell.
"We found that if we compare somebody in the top quartile of exposure with the lowest quartile of exposure, sperm concentration was on average about 23 percent lower in men with the highest BPA," Meeker said.
Results also suggested a 10 percent increase in sperm DNA damage.
Several previous studies have documented adverse effects of BPA on semen in rodents, but this is the first to report the effects of BPA on semen in humans.
The results are consistent with a previous study by Meeker and Hauser suggesting that certain hormones - follicle-stimulating hormone and Inhibin B - are elevated or decreased in relation to BPA, respectively, a pattern consistent with low sperm production and development.
Due to the study's relatively small sample size and design, the scientists say their results are "preliminary and more study is needed."
"The study from which these data came is currently in progress," Hauser said. "With a larger sample size and enhanced study design, we will be able to more definitively investigate this preliminary association in the near future."
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