This is the VOA Special English Health Report.
这里是美国之音慢速英语健康报道节目。
A mother in Washington noticed something unusual one day, just before her daughter's eighth birthday.
华盛顿市一位母亲在女儿8岁生日前的某天注意到一些异常。
MOTHER: "I noticed around the end of two thousand eight, I think she's getting breasts. This is ridiculous, she's seven, and I thought I was crazy. So, when we went for our annual check-up, I asked the doctor if I was right. And she said, 'Yeah, she has breast buds.'"
母亲：“2008年底左右，我觉得她的乳房好像开始发育了。这很荒唐，她才7岁，我想我肯定是疯了。在我们去做年度体检时，我向医生进行了咨询。她说，是的，她乳房开始发育了。
Last year a study in Denmark reported an increase in early breast development. Now a new study in the journal Pediatrics adds to evidence of an increase in early puberty in American girls.
去年丹麦的一项研究报告称，乳房提前发育的女孩数量有所增加。现在儿科杂志的一项新的研究进一步证明，发育提前的美国女孩数量有所增加。
The study took place in three big cities. Dr. Frank Biro at Cincinnati Children's Hospital Medical Center in Ohio led the study. He says it began about seven years ago.
这项研究在3个大城市进行，俄亥俄州辛辛那提儿童医院医学中心的弗兰克·比罗（Frank Biro）医生领导了这项研究。他说，这项研究大约开始于7年前。
FRANK BIRO: "We followed this group of approximately twelve hundred girls on a regular basis to see when they would enter into puberty."
比罗：“我们对大约1200名的一组女孩进行定期跟踪观察，以确定她们什么时候开始发育。”
Dr. Biro says the study found that white girls had the greatest increase in rates of breast development. The rates, he says, were about twice as high for seven- and eight-year-olds compared to earlier studies.
比罗医生称，研究发现，白人女孩乳房提前发育比例的增幅最大。对7-8岁的女孩来说，这个比例大概是此前研究数据的2倍。
At age seven, the rates were ten percent of whites, twenty-three percent of blacks and fifteen percent of Hispanics.
在7岁时，白人女孩乳房提前发育的发生比例是10%，黑人是23%，拉丁裔是15%。
Dr. Biro says girls with a higher body mass index are more likely to enter puberty early. Body mass index, or BMI, is a measure of weight in relation to height. But the nation's increase in overweight children may be only part of the explanation.
比罗医生表示，BMI指数（身体质量指数，简称体质指数又称体重指数，英文为Body Mass Index，简称BMI）越高的女孩提前进入发育期的可能性越大。BMI指数衡量身高和体重的关系。美国超重儿童数量的增加可能只是其中的部分原因。
The researchers have been collecting blood and urine samples from the girls for testing. Dr. Biro says the tests are to look for chemicals from the girls' environment that could affect growth.
研究人员采集了这些女孩的血液和尿液样本进行检测。比罗医生说，这项检测是为了从这些女孩体内寻找可能影响发育的化学物质。
FRANK BIRO: "That is, chemicals that might mimic natural hormones that our body makes, or somehow interfere with how those hormones act on the body."
比罗：“也就是说，这些化学物质可能会复制人体生成的自然激素，或者干扰激素在人体中的作用。”
He says these chemicals could include growth hormones fed to farm animals, but they could also include chemicals such as phthalates. These are used to makes some kinds of plastics and other products.
他表示，这些化学物质可能包括喂养家畜的生长激素，但是也可能包含类似邻苯二甲酸盐一类，用于制造塑料和其他产品的化学物质。
FRANK BIRO: "In addition to the types and amount of food we eat, the other important factors are some of these chemicals. For example, personal care factors, such as cosmetics, such as suntan lotions, contain certain chemicals that could impact timing of maturation or other body functions."
比罗：“除了我们吃的食物，身体护理产品等化学物质也是另外一个重要因素。像化妆品、防晒霜中就包含某些可能影响发育期或其他身体功能的化学物质。”
But it is too early to know what the tests will show.
但是，想知道测试结果究竟怎样尚为时过早。
FRANK BIRO: "We'll need to wait for all the girls to enter puberty before we have a good grasp on what the contribution is of those environmental chemicals."
比罗：“我们将必须等到所有女孩都进入发育期后，才能彻底了解这些化学物质到底起到了什么作用。”
He says less research has been done to look for early puberty in boys. But he says some studies have shown that a higher BMI does not speed up development in boys, and may even slow it.
他表示，关于男孩提前进入发育期的研究较少。但是他说一些研究已表明，BMI较高不会加快男孩的发育，但是可能会减缓其发育。