Marijuana potency increased overall over the last 20 years, says the U.S. government.

As of last year, there was only one state lab testing medical marijuana in New York

New York’s recreational marijuana battle sits on the front line of a generational war over American cannabis laws. As debate heats up, USA TODAY Network New York is compiling answers to key questions about legalized cannabis. The findings will be updated each Monday as New York considers joining the 10 states that allow adults to use marijuana.

Complex marijuana testing overhauls are straining regulators, businesses and consumers as legal cannabis use prompts new public-health warnings, experts say.

They cited contaminated cannabis reaching shelves, questionable test results at some laboratories and recent trends towards limiting marijuana potency as examples.

The ongoing evolution of cannabis testing comes as states scramble to tighten quality controls and reduce health threats amid mounting opposition to adult-use marijuana laws, including those proposed in New York.

What follows is an analysis of key cannabis oversight issues, including data from the National Institute of Health, industry experts and state authorities in several legal marijuana states.

Why pot potency matters

Knowing marijuana potency is crucial to judge its effects and is based on content of tetrahydrocannabinol, or THC, the psychoactive ingredient that produces a high.

Pre-legalization, potency levels got tested through flower-based smokable marijuana confiscated from the black market for decades.

The samples steadily increased in strength since the early 1990s, rising from roughly 7.5 percent for sinsemilla, a higher potency marijuana from specially tended female plants, to 16 percent in 2013, according to the National Institute of Drug Abuse.

Potency of more generic marijuana increased to 9.6 percent from 3.7 percent in that span.

Users smoking or eating THC-rich hash oil extracted from the marijuana plant, called dabbing, encountered much higher levels, about 50 percent on average but topping 80 percent in some tests.

During the loosely regulated earlier period of recreational marijuana post-2014, cases mounted of users sickened by extracts and edibles, like brownies and gummies.

Pro-marijuana groups then launched safe-use campaigns, including urging people to keep edibles from children and exercise caution when trying extracts, and similar concentrates.

Billboards and advertisements in Colorado warned tourists against overindulging on cannabis candy bars, according to the "Consume Responsibly" campaign website affiliated with the Marijuana Policy Project.

“If you compare marijuana to alcohol, flowers would be roughly equivalent to a light beer and concentrates would be comparable to hard liquor,” the website said.

Yet as medical officials raised new concerns about marijuana’s public safety risk, authorities in Colorado, California and other states have since started limiting potency and raising testing standards.

Marijuana quality control struggles

California’s push to tighten cannabis restrictions last year focused on removing pesticides, heavy metals and other contaminants.

The change underscored the limited product testing previously. Many businesses complained of supply shortages due to the insufficient number of laboratories capable of testing products under new rules, USA TODAY Network reported.

Further, authorities in Colorado cited challenges linked to disputable potency testing results due to lack of a universal standard method, and Oregon health officials said some their state’s cannabis labs were doctoring tests to drive business.

“Consumers are choosing based on potency results, good, bad or indifferent,” regulators reported last year. “This is driving a lot of pressure on labs to inflate potency results.”

Authorities made the comments in calling for new checks on labs to crackdown on the testing compliance issues.

Other problems in Oregon included legally made marijuana being smuggled into other states, as well as gaps in state safety inspections of growers, dispensaries and labs.

Authorities also raised concerns about Oregon’s failing to require testing of marijuana for heavy metals and microbiological contaminants like salmonella and E. Coli, which are prohibited in other states.

How NY tests marijuana

Gov. Andrew Cuomo’s hotly debated cannabis legislation includes broad rules for using independent laboratories to test the recreational drugs.

It would leave many details up to a new Office of Cannabis Management under the Division of Alcoholic Beverage Control.

Much of the plan appears to build upon testing standards established by the state’s medical marijuana program, which began selling drugs in 2016.

One key aspect to watch will be the state’s approach to certifying labs to conduct tests.

There was only one site testing medical marijuana in New York, the state's public health lab at Wadsworth Center, according to a report last year.

Regulators had repeatedly sought independent labs to apply for testing certification but failed, a common problem stemming from businesses reluctance to handle a drug still prohibited by federal law.

Meanwhile, Gov. Cuomo’s pending budget plan includes $750 million to replace the aging Wadsworth facilities with a new lab in Albany, suggesting it would remain a critical part of meeting the growing demands of medical and recreational pot testing and quality control.