"Probe finds drugs in drinking water" was typical of the headlines in the newspapers back in March 2008 when an Associated Press report revealed the results of an investigation carried out by three of its reporters. So how do pharmaceutical drugs get in drinking water? That is the question that this article will attempt to answer.

When you fill a glass with water from a tap in your home that water comes from the local public water treatment plant which draws its supply from lakes and rivers or, in some cases, groundwater from boreholes. The lakes and rivers rely on rainwater that falls on the hills and the waste water from our homes and businesses. And it is the waste water that is the major source of the drugs in our drinking water.

So how do the drugs get into the wastewater from our homes? We flush them down the toilet. This is the commonest way of disposing of out of date or unused medications. In fact it is one of the three recommended methods of disposal, the other two being to put them in the trash or to return them to a collection point.

You might think that the average individual, even if they are on regular medication, would not have that many unused pills to dispose of so that this should not be a problem. But it appears that this is the way that unused pharmaceuticals are disposed of in clinics and hospitals. A nurse with twenty year's experience reported that her clinic in a small community of 10,000 flushed down the toilet enough drugs to fill a 1lb coffee can every month.

Another report revealed that it is "unofficial" procedure in over 16,000 nursing homes in the US to flush patient medications down the toilet. Ambulance services, rehabilitation centers, and even hospitals routinely flush expired medications because it is the cheapest and easiest way to do it.

But it's not only humans who cause the problem. Animals are involved too. Cattle are routinely treated with steroids to boost productivity, but about 10% of the drug is excreted and finds its way into the water supply. In addition vets are treating pets with the same drugs as humans and so providing another source of contamination.

The good news is that any of the pharmaceuticals that have not dissolved by the time they reach the water treatment plant are trapped in the sludge that is removed as part of the filtration process. Unfortunately in some cases this sludge is then spread on farmland as a fertilizer allowing the drugs another chance to pollute the water supply.

So that is the short answer to the question "How do pharmaceutical drugs get in drinking water?". If you are concerned about drugs in your drinking water perhaps you should consider fitting a water filter in your home.