Michigan officials are urging all medical marijuana retailers to test their vape cartridges for heavy metals after a batch of them recently tested positive for lead contamination.

All of the vape cartridges were destroyed, according to officials with the Department of Licensing and Regulatory Affairs.

Previously the marijuana distillate used to fill the cartridges was tested only after it had been produced -- not in its final form after the cartridge had been filled. State regulators updated their advice to processors in a memo April 15.

Now, all vape cartridges must undergo testing after they are filled -- which includes tests for heavy metals.

Regulators are also strongly urging retailers to have the vape cartridges sitting on their shelves to undergo testing as well. Medical marijuana patients and caregivers can also take their vape cartridges to testing labs to have them checked.

Not all vape cartridges are alike: some are ceramic and others have metal components.

The cartridges made of metal are the main concern to state officials. In a study published in Environmental Health Perspectives in February 2018, the Johns Hopkins Bloomberg School of Public Health found the heating coils in e-cigarettes were leaking lead and other heavy metals into the vaping liquid -- which then made its way into the aerosol that the user inhaled.

In addition to lead, researchers found potentially unsafe levels of chromium, manganese and nickel. Inhaling those metals over time has been connected to lung, liver, immune, cardiovascular and brain damage, and some cancers, according to the study.

-- Amy Biolchini is the marijuana beat reporter for MLive. Contact her with questions, tips or comments at abiolch1@mlive.com. Read more from MLive about medical and recreational marijuana.