The day this small town told its residents to stop drinking the water, life on Glendale Boulevard turned from quiet to alarming.

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问题    The day this small town told its residents to stop drinking the water, life on Glendale Boulevard turned from quiet to alarming. One couple decided to immediately put their house up for sale. Another fretted over their young son and the baby who would soon arrive. And up the street, one mom felt a rising indignation that would turn her into an activist determined to restrict the chemicals contaminating her family’s drinking water — and that of millions of other Americans.
   That late July day, this town along the banks of the Kalamazoo River became the latest community affected by a ubiquitous class of compounds known as polyfluoroalkyl and perfluoroalkyl substances, or PFAS. For years, calls for the federal government to regulate the chemicals have been unsuccessful, and last year the Trump administration tried to block publication of a study urging a much lower threshold of exposure.
   The man-made chemicals have long been used in a wide range of consumer products, including nonstick cookware, water-repellent fabrics and grease-resistant paper products, as well as in firefighting foams. But exposures have been associated with an array of health problems, among them thyroid disease, weakened immunity, infertility risks and certain cancers. The compounds do not break down in the environment.
   In Parchment, where they were once used by a long-shuttered paper mill, tests found PFAS levels in the water system in excess of 1,500 parts per trillion — more than 20 times the Environmental Protection Agency’s recommended lifetime exposure limit of 70 parts per trillion. Local officials promptly alerted residents. Michigan officials declared a state of emergency. People started picking up free cases of bottled water at the high school. Within weeks, the town abandoned the municipal wells that had served 3,000 people and began getting water from nearby Kalamazoo. "This is not a problem you can run away from," said Parchment resident Tammy Cooper, who has become an outspoken advocate for better regulation. "There are Parchments across the country."
   Harvard University researchers say public drinking-water supplies serving more than 6 million Americans have tested for the chemicals at or above the EPA’s threshold — which many experts argue should be far lower to safeguard public health. The level is only an agency guideline; the federal government does not regulate PFAS. The compounds’ presence has rattled communities from Hoosick Falls, N.Y., to Tucson. They have been particularly prevalent on or near military bases, which have long used PFAS-laden foams in training exercises.
   Both houses of Congress held hearings on the problem last year, and lawmakers introduced bills to compel the government to test for PFAS chemicals nationwide and to  respond wherever water and soil polluted by them are found. In late November, the head of the EPA vowed that the agency would soon unveil a "national strategy" to address the situation. Affected communities are still waiting. "There are some very real human impacts from this stuff," said Erik Olson, a drinking-water expert for the Natural Resources Defense Council. "Most people have no idea they are being exposed."
   Michigan is one of the few states where officials are trying to determine the extent of PFAS contamination. Health officials undertook statewide tests this year across 1,380 public water supplies and at more than 400 schools that operate their own wells. "When we look for it, we tend to find it," said Eden Wells, the state’s chief medical executive. Yet detection raises difficult questions, given the lack of regulation involving PFAS in water and the evolving research on its long-term health effects. "Many of our responses are outstripping the scientific knowledge we need," Wells said.
   More is known about two particular types of the chemicals, perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), which companies phased out years ago amid growing evidence that both were ending up in the blood of nearly every American. But thousands of other PFAS chemicals remain in use — among the many threats, including arsenic and lead, to drinking water nationwide.
From the last paragraph, we learn that PFOS and PFOA______.

选项 A、are known by more people
B、are not PFAS chemicals
C、are no longer in use
D、are found in the blood of nearly every American

答案C

解析 细节题。根据题干关键词定位最后一段,根据定语从句的语义可知:数年前各公司便已停止使用这两种化学物质,故C为正确答案。
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