Look down next time you are near Belorussky Station, and you will see Boris’ simple ad for salt. His number is written on the ground in huge letters with the word “salt” above and “spices” below, as if he were a merchant of olden days, when salt was a valuable commodity.

It is one of hundreds of ads written on pavements that appear whenever the city’s streets are snowless and clean enough to look at, but this is an ad with a difference. You are unlikely to ever meet Boris, unless you are able to put together a good surveillance team.

Maybe lots of people ring up Boris asking for real salt and spices, but the ad is not for them. It is for those who understand immediately from those two words that Boris is a drug dealer, who is selling bath salts and smoking powders, the use of which, drug prevention workers say, has become an epidemic in Russia.

Boris did not answer on first call, ringing back from a number that did not reveal itself. Thinking he was speaking to a customer, he explained how it worked.

A packet of salt costs 2,500 or 3,500 rubles, and payment has to be made beforehand. It is brought in from abroad, he said, as are the spices, and then comes down from St. Petersburg.

“You know Qiwi,” he said, referring to the telephone payment terminals all round the city. You have to put the money on an account there and then wait for delivery, he said.

Here Boris’ system gets even cagier as the courier, who is not Boris, will go to your nearest metro station and leave the parcel somewhere for you to pick up. You won’t have a face-to-face with him either.

Still, Boris didn’t seem too worried about the police catching him and chatted away, asking how much drugs cost in England.

He had a good system, he said. “Nobody meets anyone,” although he did admit that putting an ad in the center of the city was “cheeky.” His ads are all over the city, he said. He only works till 11 as his couriers use the metro.

It is possible that it is a scam, and the money will disappear into Boris’ pocket, but selling “salt,” which has an uncertain legal basis in Russia, is big business these days and Boris is far from being the only one to sell it.

These ads have been seen all over the Urals by bloggers. One ad was seen on the wall of an Ufa pedagogical university, and volunteers from a Christian youth organization sprayed over ads near Domodedovo last week, after police ignored complaints about the drug ads.

“Salt” use is not only limited to Russia, and there have been reports in the United States and Great Britain of serious drug abuse and of its horrendous side effects.