[Author Neal McGrath recently attended the Green Pharma Summit for GreenBiz.com; this is his second report from the event; to read his case study of McKesson's sustainability project, see "Scaling up Sustainability at McKesson."]

At a recent gathering of sustainability people from some of the world's largest pharmaceutical companies (or "Environment, Health and Safety" people as they tend to be called in the pharmaceutical industry), I got a glimpse of what could be the next headache for the oft-beaten up industry. This insight came not from what they talked about the most, but rather what they did not talk about enough: The question of pharmaceutical residue in the water supply.

Over the two-day conference, one person after another presented detailed information on the tremendous progress their organizations have made in reducing the use of toxic chemicals in the manufacturing process by finding less toxic -- and sometimes even benign -- alternatives; how they have driven down energy use at their facilities and in so doing cut greenhouse gas emissions; and other impressive "greening" efforts. They spoke proudly of these accomplishments, as well they should: These gains are impressive and the questions posed by peers following each presentation showed that everyone in the room had devoted a lot of time to tackling the same issues.

But when the discussion moved to the question of trace amounts of pharmaceuticals in the water supply, everything seemed to go off the tracks.

First, there was spirited discussion of programs under which the pharmacies that sell prescription and over-the-counter medications would have to take them back. This reduces the likelihood of people flushing unused drugs down the toilet or tossing them into the trash, where they leech from landfill into the water table. This has been done in some European locations with mixed success: Lackluster results in some locations were blamed on poor public education.

Here in the U.S., the solutions are not so easy. Many drugs are controlled substances and it is not clear that pharmacies are legally allowed to take them back. The EPA may support the approach, but the DEA is less enthusiastic: Drugs are carefully controlled on their way out the door but there are no such controls or even procedures to handle these drugs when they come back.

And while a pharmacist earning $90,000 per year may not risk his license to divert returned pharmaceuticals into his own pocket (or sell them), what about the $10-an-hour pharmacy technician who is not licensed? Some small pharmacies have launched pilot programs to test prescription takebacks, but the big national chains don't like the idea.

Other ideas such as having local law enforcement serve as collection points were also discussed, but that approach has its own limitations. The police are busy maintaining law and order, can they also be asked to manage waste disposal? Sure, they can hold onto a small quantity of drugs taken from a suspect and hold it as evidence, but can they be asked to manage hundreds of pounds of pills that include everything from antibiotics to OxyContin?

Then the real challenge made its way into the discussion: What is the source of the trace amounts of pharmaceutical products being found in water supplies? Some conference attendees confidently stated they must coming from people tossing unused pills into the toilet; if they are right, then some kind of take-back program is a good solution, however tricky it may be to implement.

Others were not so confident or the contamination's source; they asserted with equal conviction it was coming from human excretions. Since most drugs don't completely metabolize in the body, a little or a lot (depending on the drug) is released in the patient's urine. If this is the source, take-back programs won't do anything to solve the problem.

The biggest and most looming challenge seemed to be that the people in the room did not agree on this basic question, and it turns out that the few studies done so far have also not delivered clear answers.

This is clearly a challenge: If you don't know the source, how can you devise an approach to tackle it?

And this is scary stuff, both from a health perspective and for the industry itself: The public can be counted on to react with emotion and not well-thought-out reason. A situation like this can also be easily grabbed by the media and turned into a sensational story. Activists will seize the issue and use it as a baseball bat to beat up on their favorite scapegoats. And let's face it, the pharmaceutical industry is one that many of them love to hate.

I thought of the challenges Monsanto faced when, much to its chagrin, environmentalists were not elated that the company's genetically modified crops would help feed the world's hungry and instead vilified them for creating "Frankenfoods."

I thought also of the industry response to concerns about vaccines and autism. There is no scientific evidence to support this theory, yet after years of insisting there is no connection (a position supported by the CDC), the industry eliminated the use of thimerosal in vaccines, the ingredient pointed to by many as the culprit. This put the industry in the uncomfortable position of having to maintain that thimerosal was never a problem, while also explaining why they stopped using it.

Yikes.

Right now, drug stores are the ones bearing the brunt of this issue. But how long will it be before attention turns to the pharmaceutical industry? Seven states already have proposed legislation to mandate take-back programs, while the state of Maine is limiting how big a supply doctors can prescribe for first-time users of certain medications. France has a mandatory program that is paid for by the industry. I expect it won't be long before the conversations about this hot potato subject turn more serious.

Neal McGrath is the director of Green Tree Communications, a sustainability consulting company based in New York City.

Photos CC-licensed by Flickr users e-magic and Fillmore Photography.