As covered in the first two parts of this series, a dangerous—and mysterious—new cutting agent called levamisole has entered the cocaine supply. It's being cut into cocaine in Colombia (meaning that local dealers probably don't know any more about this stuff than you do). Levamisole is a medicine typically used to deworm livestock (cows, pigs, horses), but in humans it can trigger a catastrophic immune-system crash called agranulocytosis. Basically, levamisole can obliterate your white blood cells, leaving you vulnerable to infections. It's impossible to pin down exact numbers, but in the past few years, people have been hospitalized and several have died due to levamisole poisoning.

Several sources—from federal government agencies to local doctors at Harborview Medical Center who are testing cocaine and cocaine users—estimate that around 70 percent of the U.S. cocaine supply is cut with levamisole. It's everywhere, from Seattle to France to the UK.

Typically, it's difficult for drug users to reliably test their drugs for impurities—it requires expensive, unstable, and sometimes dangerous chemicals used in laboratory conditions. But when Nathan Messer, head of the local drug-harm-reduction group DanceSafe, got in touch with a doctor in Seattle named Mike Clark (a psychiatrist and molecular biologist at Harborview) about levamisole, Dr. Clark had a moment of inspiration. He was already familiar with levamisole. He'd been using it in his lab for years, as a way to block an enzyme that interferes with certain color-change reactions in tissue samples. (Technically speaking, levamisole inhibits most types of mammalian alkaline phosphatase—it slows the enzyme to a crawl, preventing it from working.) Dr. Clark's idea was to inhibit the enzyme and then test for the inhibition.

The result: DanceSafe and Dr. Clark created an easy-to-use kit out of inexpensive materials that tests for levamisole. The Stranger is paying for some of the materials, helping to distribute the kits, and collecting anonymous data about what we learn.

Basically, you use the kit to reproduce the same chemical/enzyme reaction in two vials right next to each other. One is a test vial for your sample (powder cocaine, crack, or any other substances you'd like to test for levamisole contamination), and one is a control vial to compare against the test vial.

Follow the instructions to the right.

If the vial with the cocaine/crack in it doesn't turn yellow after you follow the instructions, that means your sample is contaminated with levamisole. (Levamisole inhibits the chemical reaction that would normally turn yellow.) If both vials turn yellow right away, your sample is not contaminated with levamisole.

The test is semiquantitative—meaning it can only roughly tell you how much levamisole is in your sample. Levamisole inhibits the reaction but doesn't stop it entirely—eventually, your test vial with the sample will turn yellow, no matter what. The faster your test vial turns yellow, the less levamisole you have (because little amounts of levamisole will only slow the reaction a little), but you'd need a spectrometer to accurately detect how much levamisole is in the sample.

• The People's Harm Reduction Alliance at the University District needle exchange: 1415 NE 43rd St (behind the post office on the Ave), 330-5777, www.peoplesharmreductionalliance.org. It's open Tuesday and Thursday from 5:00 to 7:00 p.m., and Friday and Sunday from 1:00 to 5:00 p.m.

• DanceSafe: To get kits, e-mail seattlecoke@dancesafe.org or call 888-636-2411, option 1. Dance- Safe will coordinate kit-distribution tables around the city, including Pioneer Square. This Friday evening, November 12, find them near the pergola at First Avenue and Yesler Way. Check Slog for future locations and updates.

• Capitol Hill: Volunteers will be handing out kits in the Pike/Pine corridor on Friday and Saturday, November 12 and 13, between 8:00 and 10:00 p.m.

The symptoms of levamisole poisoning are frustratingly broad—levamisole makes your body susceptible to all sorts of infections. You might have a fever, sores (especially in your mouth or anus), rashes, diarrhea, vomiting, a thick coating on your mouth and tongue, lesions, or other symptoms.

If you suddenly become ill and have been using cocaine, DO NOT hesitate to see a doctor and BE HONEST about your drug use. A doctor's primary interest is to help you get well, not turn you over to the police. As Dr. Geoff Baird at Harborview said in the most recent Stranger article about levamisole: "It is not our job to arrest patients or police them or enforce those sorts of laws."

Another benefit to being honest about your drug use: Patients who have unexplained immune-system crashes sometimes get a bone-marrow biopsy, which involves shoving a thick-bore needle into your pelvis. This is unpleasant. Fess up to your cocaine use, and you'll probably get a blood or urine test instead.

Technically, any device that "tests" an illegal substance (for purity, strength, adulterants, whatever) is considered drug paraphernalia, and use of drug paraphernalia is a misdemeanor under Washington State law. But The Stranger and the ACLU have had discussions with city attorney Pete Holmes and county prosecutor Dan Satterberg, who said they consider the levamisole test kit to be more of a public-health benefit than a criminal menace.