The results of the United Nations 2007 World Drug Report, showing Canada leading the industrialized world in marijuana consumption, need to be interpreted with caution, to the UN body that did the drug study says.

For one thing, only 104 of 192 countries asked to participate in the study did so. Second, the reliability of the reporting data from those 104 countries wasn't uniformly reliable.

It's not easy to measure drug use objectively. The UN study relied on self-reporting surveys, which can't always be trusted.

The only drug for which truly objective consumption data can be obtained is cocaine, the result of new testing technology that allows for the examining municipal waste water.

According to this process, scientists look for evidence of a chemical called benzoylecgonine. Since this chemical does not come from any other source than the organic processing of cocaine, it is considered a reliable indicator of cocaine consumption.

According to the World Drug Report's appendix on methodology, "the assumption is that cocaine that has been consumed is eventually leaving the human body and - in developed areas - (that) most of this will land in waste-water systems in the form of benzoylecgonine."

"It's a very credible testing mechanism," said Jurgen Rehm, senior scientist with the Toronto-based Centre for Addiction and Mental health.

So, who, by this measure, is the cocaine king of the world, or at least the industrialized world?

Waste-water tests that started in Italy in 2005 and later conducted elsewhere found benzoylecgonine concentrations in New York City's waste water far higher than in any other single city in the world. The different concentrations were translated into estimated lines of cocaine consumed per 1,000 people age 15 to 64.

By that measure, New York registered 134 lines per 1,000 people. Next were Mirana de Ebro, in Spain (97 lines), and Washington, D.C. (56).

There were no Canadian cities in the Top 25 list.

(Rolo's Commentary: Guess this means we have to work that much harder folks!!)