Drugs have the capacity to do significant environmental harm when they pass through the human body and wash down the drain. Millions of prescriptions are filled each year, and about 40 percent end up being improperly discarded. As of 2008, according to the Associate Press, drinking water is tainted with many drugs. The potential long-term consequences remain unclear, but chemists are taking steps to reduce pharmaceutical drugs' environmental impact. For those looking to entering the pharmaceutical industry, the challenge is to develop environmentally sound products that are also effective. In many cases, altering a drug to make it more environmentally friendly can significantly alter its most beneficial medical properties. Scientists believe that one possible way to fix the problem is by creating "benign-by-design" drugs. These drugs are bioactive and resistant to degradation, which makes them stable and effective. However, it also increases their half-life, which allows them to persist in the environment long after they have been used. Chemists are also looking at drugs currently on the market that by nature have greener properties. Glufosfamide, a drug used to combat pancreatic cancer, is one drug that biodegrades easily. Valproic acid, which is used to control epilepsy, is another biodegradable drug. A class of drugs called biologics, which include insulin and most vaccines, contain a large volume of natural compounds, which makes them break down more quickly in the environment. Other drugs, notably Viagra, are converted by human bodies into less powerful metabolites. This means that they enter the environment much more diluted than other drugs. In addition to studying the consequential biodegradable properties of some pharmaceuticals, scientists are trying to figure out a way to make drugs potent until they pass through the body, and then biodegrade upon entering the environment. One possible way for them to accomplish this is by making drugs more photodegradable, or light-sensitive, so that they break down in waste treatment facilities. Chemists are also considering creating drugs that are less stable but partnered with a temporary stabilizer, so that they become biodegradable after exiting the body. Another possibility for chemists is to make drugs more potent, which in turn reduces dosage amounts, and will put fewer drugs into the surrounding environment. A bonus for patients is that a lower dosage could reduce the likelihood and intensity of side effects. With the advent of technology, which makes treating certain conditions more precise, this may be a good possibility. This is particularly true with cancer treatment, as newer cancer treatments are targeting malignant cells more accurately now than in the past. When evaluating the potential for drugs to be more environmentally friendly, chemists use Lipinski's Rule of Five, which identifies molecular features that make a drug orally active, as a standard. To date, no drug has the equivalent ecotoxicity, but researchers are looking for ways to redesign molecules to make them less environmentally damaging. Some chemists have started to tackle this problem by adding ester bonds to molecules, which makes them more biodegradable. Chemists may also start avoiding quaternary carbons, which are saturated carbons in an organic species that are bonded to four carbon atoms. Because of their properties, quaternary carbons reduce biodegradability by organisms. According to pharmaceutical representative Berkeley W. "Buzz" Cue Jr., one way to make drugs less environmentally destructive is to increase their oral availability, which makes them pass through the body less easily. Cue estimates that, on the present market, up to 80 or 85 percent of drugs have poor bioavailability. Lipitor, for instance, only has a 12 percent biodegradability rate. One potential way to solve the problem, he believes, is to remove moieties like blocking groups that chemists add to synthesize drugs. These properties, which are not required for activation, can be removed to reduce the drugs' environmental footprints. For the pharmaceutical industry, unlike other industries that sell products to consumers, there is little incentive to make greener products. One of the only benefits for major drug companies would be to produce drugs with an additional marketable benefit, such as the reduction of side effects. It takes drug companies a long time to develop and design drugs, and finding other ways to modify them adds to the cost and time of production. Some progress has been made in Europe to work on environmentally friendly drugs, but it could take some time before the trend catches on elsewhere.