Marijuana testing has historically been used to verify whether a person has the substance in their system. But as more states legalize the drug for recreational and medical purposes, there is a growing need to test marijuana for different reasons — to verify its safety, purity, potency and active ingredients.

Part of the push to begin laboratory testing on marijuana came after Washington and Colorado legalized the substance for recreational use in November 2012. According to a report in the Associated Press, the action “has placed regulators and researchers in a race against time to develop health warnings and ratings for potency before the legalized dispensaries open in the states.”

Just like alcohol, when retail sales of marijuana begin next year in the two states, the drug will come with health warnings, potency ratings and certification that it meets the safety limits for pesticides, molds and microbes such as E. coli and salmonella.

Regulators say they want to ensure people are aware of just how strong the drug is before they use it and don’t want people getting enormous doses at once. For these reasons, the concentrations, chemical compositions and active ingredients will all be labeled on the product.

Genifer Murray, the CEO of CannLabs in Denver, said the drug needs to be properly dosed, especially when it is being used medicinally.

“You can’t just say take a few puffs every few hours,” she said. “You can’t die from eating cannabis, but you sure can feel like dying if you eat too much.”

The tests will be expensive, adding about $500 to the cost of every 5 pounds of marijuana, which currently costs between $1,500 to $3,500 for 1 pound, according to the AP. But Murray says the extra cost is worth it because regulators will be able to trace contaminated marijuana back to the source.

Mason Tvert, the spokesman for the Marijuana Policy Project, said the decision to test the safety of marijuana “demonstrates a shift in how we are beginning to treat marijuana in this country.”

“Legal products are regulated and sold in a controlled marketplace. And that’s what we are going to see — are already beginning to see — with marijuana, be it for medical purposes or simply for adult use,” he said to the AP.

Though the main focus of the safety testing appears to be related to potency levels, some states — especially those that have legalized marijuana only for medical purposes, like Oregon — have expressed interest in testing the drug for pesticides and other chemicals.

Even though the tests on chemicals may be limited at first, Dr. Alan Bates, a state senator who supported Oregon’s new law and a family doctor who prescribes marijuana, said testing is good news for patients.

“I’m especially worried about pesticides being inhaled or ingested,” Bates told the AP. “We should treat it as a medical thing. If I told you there were herbicides and pesticides inside regular medication, I don’t think people would be happy about that.”

Because marijuana is often inhaled and not eaten, the pesticides on the plant are more likely to be directly transmitted to the lungs and the bloodstream.

As Mint Press News previously reported, pesticides may be used on marijuana plants much more frequently than the public expects, and the chemicals may cause severe harm when ingested by users.

“John,” an insider at the California Department of Food and Agriculture who spoke to Mint Press on the condition of anonymity, said that growers often use pesticides to ensure the survival of the plant and to make them bloom faster. This is one reason growers are often opposed to the legalization of marijuana, he said. Once marijuana is legalized, the government will likely begin to regulate the pesticides used, and growers would no longer be able to rely on this technique to increase their marijuana supply, the source said.

Jeff Raber works at The Werc Shop, a lab that tests products primarily for California medical marijuana dispensaries in Pasadena, Calif.

“There’s a pretty considerable amount of contaminated cannabis,” he said to the Huffington Post. “There are no application standards.”

“Since we’re not telling growers that they’re allowed to use anything, they often use whatever they can get their hands on. And that’s a lot of bad things,” he added.

Tests on medical cannabis samples in Los Angeles earlier this year were found to contain pesticide residues at levels 1,600 times the legal digestible amount. Raber said this is concerning, especially for medical marijuana patients who have a liver disease.