US manufacturers, including major drugmakers, have legally released at least 271 million pounds of pharmaceuticals into waterways that often provide drinking water -- contamination the federal government has consistently overlooked, according to an Associated Press investigation.

Hundreds of active pharmaceutical ingredients are used in a variety of manufacturing, including drugmaking: For example, lithium is used to make ceramics and treat bipolar disorder; nitroglycerin is a heart drug and also used in explosives; copper shows up in everything from pipes to contraceptives.

Federal and industry officials say they don't know the extent to which pharmaceuticals are released by US manufacturers because no one tracks them -- as drugs. But a close analysis of 20 years of federal records found that, in fact, the US government unintentionally keeps data on a few, allowing a glimpse of the pharmaceuticals coming from factories.

As part of its ongoing PharmaWater investigation about trace concentrations of pharmaceuticals in drinking water, AP identified 22 compounds that show up on two lists: the EPA monitors them as industrial chemicals that are released into rivers, lakes and other bodies of water under federal pollution laws, while the Food and Drug Administration classifies them as active pharmaceutical ingredients.

The data don't show precisely how much of the 271 million pounds comes from drugmakers versus other manufacturers; also, the figure is a massive undercount because of the limited federal government tracking.

To date, drugmakers have dismissed the suggestion that their manufacturing contributes significantly to what's being found in water. Federal drug and water regulators agree.

But some researchers say the lack of required testing amounts to a 'don't ask, don't tell' policy about whether drugmakers are contributing to water pollution.

"It doesn't pass the straight-face test to say pharmaceutical manufacturers are not emitting any of the compounds they're creating," said Kyla Bennett, who spent 10 years as an EPA enforcement officer before becoming an ecologist and environmental attorney.

Pilot studies in the US and abroad are now confirming those doubts.

Last year, the AP reported that trace amounts of a wide range of pharmaceuticals -- including antibiotics, anti-convulsants, mood stabilizers and sex hormones -- have been found in American drinking water supplies. Including recent findings in Dallas, Cleveland and Maryland's Prince George's and Montgomery counties, pharmaceuticals have been detected in the drinking water of at least 51 million Americans.

Most cities and water providers still do not test. Some scientists say that wherever researchers look, they will find pharma-tainted water.

Consumers are considered the biggest contributors to the contamination. We consume drugs, then excrete what our bodies don't absorb. Other times, we flush unused drugs down toilets. The AP also found that an estimated 250 million pounds of pharmaceuticals and contaminated packaging are thrown away each year by hospitals and long-term care facilities.

Researchers have found that even extremely diluted concentrations of drugs harm fish, frogs and other aquatic species. Also, researchers report that human cells fail to grow normally in the laboratory when exposed to trace concentrations of certain drugs. Some scientists say they are increasingly concerned that the consumption of combinations of many drugs, even in small amounts, could harm humans over decades.

Utilities say the water is safe. Scientists, doctors and the EPA say there are no confirmed human risks associated with consuming minute concentrations of drugs. But those experts also agree that dangers cannot be ruled out, especially given the emerging research.

Two common industrial chemicals that are also pharmaceuticals -- the antiseptics phenol and hydrogen peroxide -- account for 92 percent of the 271 million pounds identified as coming from drugmakers and other manufacturers. Both can be toxic and both are considered to be ubiquitous in the environment.

However, the list of 22 includes other troubling releases of chemicals that can be used to make drugs and other products: 8 million pounds of the skin bleaching cream hydroquinone, 3 million pounds of nicotine compounds that can be used in quit-smoking patches, 10,000 pounds of the antibiotic tetracycline hydrochloride. Others include treatments for head lice and worms.

Residues are often released into the environment when manufacturing equipment is cleaned.

A small fraction of pharmaceuticals also leach out of landfills where they are dumped. Pharmaceuticals released onto land include the chemo agent fluorouracil, the epilepsy medicine phenytoin and the sedative pentobarbital sodium. The overall amount may be considerable, given the volume of what has been buried -- 572 million pounds of the 22 monitored drugs since 1988.

In one case, government data shows that in Columbus, Ohio, pharmaceutical maker Boehringer Ingelheim Roxane Inc. discharged an estimated 2,285 pounds of lithium carbonate -- which is considered slightly toxic to aquatic invertebrates and freshwater fish -- to a local wastewater treatment plant between 1995 and 2006. Company spokeswoman Marybeth C. McGuire said the pharmaceutical plant, which uses lithium to make drugs for bipolar disorder, has violated no laws or regulations. McGuire said all the lithium discharged, an annual average of 190 pounds, was lost when residues stuck to mixing equipment were washed down the drain.