The end of the year is also becoming the end of synthetic marijuana sales in Illinois. Last week, Chicago's ban on fake pot went into effect just ahead of the state law that takes hold Jan. 1.

The Chicago ordinance bans the sale of products containing any of five hallucinogenic substances and fines businesses between $500 and $1,000, with each day a retailer continues to carry it a separate offense. The state law makes possession or sale of those products a felony. "By including all of the chemical compounds commonly found in synthetic marijuana, this ordinance will allow us to proactively stay ahead of this behavior and send a clear message to irresponsible merchants who are selling these products out in the open that this will no longer be tolerated," said Chicago Mayor Rahm Emanuel.

Illinois joins at least 40 other states that have passed laws or written departmental rules to ban synthetic cannabinoids, according to the National Conference of State Legislatures. Sometimes called K2 or Spice, the products at issue are a mix of herbs and spices usually sprayed with synthetic cannabinoids. The effects can include anxiety, vomiting, seizures and hallucinations. The products are marketed toward teens and young adults, and retailers often emphasize that the drugs won't show up in routine urinalysis tests, according to the Drug Enforcement Agency (DEA).

As of Sept. 27, the American Association of Poison Control Centers had fielded 1,500 calls related to products containing synthetic marijuana. The Illinois Poison Control Center received 70 calls about the products in 2010 and 53 during the first quarter of 2011.

In March, the DEA classified synthetic cannabinoids as a temporary Schedule I drug, making it illegal to possess or sell the products for one year — with a possible six-month extension. "Young people are being harmed when they smoke these dangerous 'fake pot' products and wrongly equate the products' 'legal' retail availability with being 'safe,'" said DEA Administrator Michele Leonhart in a statement. "Parents and community leaders look to us to help them protect their kids, and we have not let them down."