Pregnant women told to drink bottled water in West Virginia area NEW: West Virginia mother says warning makes her not want to let young son drink water CDC: Because little is known about chemical, pregnant women should continue to drink bottled water Immune systems of pregnant women are more susceptible to sickness, CDC says The chemical, 4-methylcyclohexane methanol, spilled into a river (CNN) -- Health officials are advising pregnant women who live in the areas of West Virginia where a chemical leaked into the water supply last week to continue drinking bottled water. The Centers for Disease Control and Prevention gave the guidance for two reasons, spokeswoman Barbara Reynolds told CNN Thursday. First, because there has been such scant research on the chemical -- 4-methylcyclohexane methanol -- there's little understanding of what it could do to a fetus. The second is because pregnant women's immune systems are more susceptible to infection. There's no reason to take a risk and allow pregnant women to drink the water that has been cleared for ingestion by the general population without 100% certainty that there is no presence of the chemical in the water, Reynolds said. The problem stemmed from a leak of several thousand gallons of 4-methylcyclohexane methanol from a storage tank belonging to a company called Freedom Industries. That chemical, which is used in the coal industry, leaked out of a storage tank at a Freedom Industries facility, breached a concrete wall surrounding the tank, seeped into the soil, made its way to the Elk River, entered a water plant about a mile upstream and got into the water system. Last week, residents of nine counties -- including the one that's home to Charleston, West Virginia's capital and most populated city -- were urged not to use their tap water, or do anything except flush their toilets. A strong licorice odor was the telltale sign that the chemical was present, and officials warned that they couldn't say the water was safe. News of the leak broke January 9, but it's unclear if that's when the leak began. Angry mother Charleston mother Jacqueline Bevan told CNN Thursday she's not going to let her 7-year-old drink the water even though she's been told by officials that it's safe. "If a pregnant woman can't drink this... no, we're not feeling safe here in West Virginia," she said, adding that the caution about pregnant women feels like "more disturbing news." It "most upsets us" that "we're not given any details about this chemical," she said. The public hasn't been given much information about 4-methylcyclohexane methanol. She and others want to know about the chemical's long-term effects. Elizabeth Scharman, West Virginia's poison control director, told CNN last week that the chemical had not been studied. "We don't know the safety info, how quickly it goes into air, its boiling point," Scharman said. The chemical is used to wash coal before it goes to market to reduce ash. Exposure to it can cause vomiting, dizziness, headaches, diarrhea and irritated skin, among other symptoms, the American Association of Poison Control Centers and CNN's previous reporting shows. READ: What is 4-methylcyclohexane methanol Saying that there's little research on the chemical is not good enough for Bevan and other residents, she said. "This story is going to go away," she said, but health concerns among West Virginians will linger for a long time. Bevan said she wants more explanation from officials about the chemical and she wants Gary Southern, the president of Freedom Industries, to make another visit to the area talk to people. Independent testing and what the state says On Wednesday, independent testing of water supplies from a hotel and a home in southwest West Virginia showed the presence of 4-methylcyclohexane methanol, but both samples tested at levels believed to be acceptable for consumption. CNN commissioned the study, which was conducted by TestAmerica, a private company. More than half of the 300,000 West Virginians who hadn't been able to turn on their faucets since last week now have access to safe water again, the state said. Wednesday night, Laura Jordan, external affairs manager for West Virginia American Water, said that about 51,000 customers -- or 153,000 people -- have had their "do not use" water order lifted. According to the TestAmerica study, samples taken Tuesday showed the presence of 4-methylcyclohexane methanol well below the 1 part per million considered safe to drink. Water in the private residence tested at 0.27 parts per million, or about a fourth of the limit, while water at the hotel tested at .011 parts per million, roughly a hundredth of the limit, according to the testing firm. A question of regulation? Freedom Industries supplies products for the coal-mining industry. A state environmental inspector visited the site in 2010 after a complaint about an odor, said Randy Huffman, the head of the West Virginia Department of Environmental Protection. "We went out on site and didn't find anything that would cause concern, no leaks or anything like that," Huffman said. The licorice smell given off by the chemical that spilled, 4-methylcyclohexane methanol, can emerge when it is transferred to or from the facility -- not just during a leak. In 2012 inspectors visited the plant again to ascertain whether any processes had changed that would require the company to obtain additional air quality permits, Huffman said. The inspectors decided no new permits were needed, and they wouldn't have inspected the tanks where Thursday's leak occurred, he said. "There's not necessarily the kind of robust environmental controls that people might anticipate that there should be on these types of facilities," he said. That's left West Virginia officials trying "to beef up what could be viewed as a loophole with these kinds of facilities." Before 2010, the last inspection at the site had been in 1991. That inspection took place because the Charleston plant stored different materials that required regulation, said Tom Aluise, spokesman for the environmental protection department. State environmental officials said the facility had the only permit it was required to have: an industrial storm water permit. Those were the only regulatory requirements," Huffman said. The company was responsible for maintaining the tanks, Huffman said. Two U.S. congressmen contend that the spill exposes regulatory gaps in the country's chemical control laws. Booth Goodwin, the U.S. attorney in Charleston, said he's investigating whether any laws were broken when the chemical leaked into the Elk River. READ: Spill shines spotlight on loose regulation CNN's Miriam Falco and Catherine Shoichet contributed to this report