But what's in the drugs? (From Observer Magazine)

I received an assortment of street drugs purchased by The Observer journalist, and I weighed the contents then analysed them for their drug content and purity.

These figures show that the amount you get for your money can vary considerably from one location to another, and a half-gram deal can contain as little as one-tenth of a gram. His haul in Edinburgh included a bag of heroin containing 0.04g - less than one-twentieth of a gram.

The purity also varied very considerably with some 'heroin' being mainly pulverised stone and glass. There is no way of knowing what the purity is when the drugs are being bought.

Casting the issue of legality to one side, drug users are being exploited in a way that no trading standards would allow if this were any other consumer commodity. What's more, using drugs of unknown quality is highly dangerous. It can easily lead to health problems or inadvertent overdosing.

If you're used to 'scoring' 'low purity' heroin, and you inject 90 per cent, it could prove fatal. The National Drugs Helpline put drug users in touch with us at SureScreen for any technical help, so we have to be hands-on professionals giving help that is easy to understand.

As a forensic scientist specialising in drug-related cases, I now feel that drug users should be encouraged to test their drugs. We are looking at making a little, automated device to test ecstasy tablets. We have shied away from this sensitive issue, but we now feel the home-testing market is ethically justified.

Those other elements in full

Heroin: Nutmeg, brick dust, stone, glass... anything from the dealer's yard, as long as it maintains a persuasive colour.

Ecstasy: Traditionally, with white tablets: food dye, starch, talcum powder. But now different colours have started to appear on the market in part, I imagine, because it allows the dealers to throw in all sorts of stuff. The white colour was at least some sort of protection.

Cocaine: Sugar, flour, talcum powder, starch, even calcium silicate (used on arm injuries). And, in terms of the "active" ingredient, increasingly you will now have cheaper amphetamines (speed) instead of cocaine.

· Jim Campbell is a forensic scientist at SureScreen Labs, Derbyshire

Drugs Uncovered: Observer special
Drugs Uncovered

News and comment
21.04.2002: Revealed: Britain's drug habit
21.04.2002: Leader: Time to be adult about drugs

Exclusive Drugs Uncovered poll
21.04.2002: The poll: What you take ... and what you think

Introduction
21.04.2002: Mark Kohn: Boom or bust?

The knowledge
21.04.2002: The lowdown, drug by drug
21.04.2002: 100 years of altered states
21.04.2002: How much do children know?
21.04.2002: Tales of experience

Street market
21.04.2002: Drugstore Britain
21.04.2002: In the lab: What's in the drugs?
21.04.2002: My drugs
21.04.2002: Sylvia Patterson: Cocaine nation

Staying clean
21.04.2002: Martin Bright: can you kick addiction?

Class A capitalists
21.04.2002: Faisal Islam: who reaps the profits?
21.04.2002: Tony Thompson: Deadly cargo

The future?
21.04.2002: Andrew Smith: Can drugs make you smarter?
21.04.2002: The next Big High?

Drugs policy debate
24.03.2002: Rowena Young: What do we do when the drugs war stops?
24.03.2002: Blair 'must scrap failed drug tactics'
03.03.2002: Mary Riddell: The private hell of a very public death
08.07.2001: Cristina Odone: Don't legalise drugs
25.11.2001: Arnold Kemp: Prohibition should be banned
29.07.2001: Henry McDonald: Legalise drugs, but tax them too
22.07.2001: The drugs debate: where next?
20.01.2002: Viv Evans: Why Eton's drug policy is wrong
18.11.2001: Toby Young: Fed up with media cant about cocaine
28.10.2001: Euan Ferguson: But there's only one problem. I hate dope
28.10.2001: Andrew Rawnsley: New Labour is for U-turning

Britain's hard drugs epidemic: Observer investigation
15.07.2001: David Ros