Moving the black market in marijuana into the light has been a boon for state tax coffers, entrepreneurs and cannabis users, but an inconvenient fact went unaddressed in the process: Potentially dangerous chemicals are used to grow it.

That changed last fall, when a Colorado newspaper’s investigation found shelves stocked with products grown using pesticides that hadn’t been approved for cannabis farming, spurring a rush of legal, regulatory and business activity.

Since then, states have quickly drawn up regulations, companies have seen their products and methods put under the microscope — sometimes taking big hits to their businesses — and cannabis product and pesticide buyers have filed lawsuits against their manufacturers.

There is even concern that the Federal government could intervene out of concern for public health, stalling the spread of cannabis legalization and the growth it has fostered.

“If the feds wanted to crack down, we’ve given them all the reasons to,” said Nic Easley, Comprehensive Cannabis Consulting founder and chief executive, who has helped more than 60 cultivators develop their growing practices.

Little long-term research on cannabis-related pesticide risks

The use of pesticides in marijuana cultivation attracted widespread attention in September, when the first of 25 recalls of cannabis products over five months in Colorado was announced. The recalls followed a September Denver Post investigation that found pesticides the state hadn’t approved for marijuana farming on products sold at dispensaries.

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Little long-term testing has been performed on the dangers of eating or smoking products made with cannabis and grown using pesticides, so the extent of the hazard they pose is mostly unknown. Still, legalization experts worry that those unknowns could endanger the burgeoning legal marijuana industry in the U.S.

Experts say the risk is partly a byproduct of the haste to create growing capacity after legalization, which has attracted growers inexperienced with large-scale and indoor farming and led to cultivation environments that require pesticide use to sustain yields and keep plants alive. Many states also lacked pesticide regulations at the time of legalization, leaving growers without guidance.

While the Justice Department has essentially left states to manage their own marijuana enforcement, it also threatened intervention if states fail to prevent “the exacerbation of other adverse public health consequences associated with marijuana use,” according to a 2013 memo. The Justice Department did not reply to multiple requests for comment.

California was first to legalize medical marijuana in 1996; it is now legal in 23 states. After Colorado and Washington passed the first recreational marijuana legalization laws in 2012 — it’s also legal in Oregon, Alaska and the District of Columbia — a “green rush” to enter the industry began.

Some climates in states where marijuana is legal — including Oregon, Washington and Colorado — require it to be cultivated indoors, said Rodger Voelker, lab director at cannabis testing service Oregon Growers Analytical. The combination of an indoor climate and overplanting can lead to “stressed” plants more likely to develop fungus and mites, Voelker said.

Growers have turned to pesticides — such as myclobutanil, which breaks down into an asphyxiant that can cause various forms of sickness when burned, and the insecticide imidacloprid — that have been used on such ornamental crops as roses and Kentucky bluegrass, as well as edible crops in regulated amounts, according to Easley.

But no long-term studies of the effects of inhaling those chemicals by smoking them have been conducted, according to experts. Pesticide use on marijuana crops, meanwhile, has been “rampant,” according to Brian Smith, communications director for the Washington State Liquor and Cannabis Board, even as the health implications remain unclear.

“There’s no research on what any of this means,” said Smith.

The EPA worries about ‘unknown health consequences’

The Environmental Protection Agency ultimately approves the use of pesticides on crops, but states can do their own testing, draft guidelines for growers within their borders, and propose pesticides for federal testing and approval. As of February, no state had submitted a complete application for pesticides to be used to grow marijuana, according to the EPA.

“The use of unregistered pesticides on marijuana may have unknown health consequences, as no pesticides have undergone complete risk assessments for use on marijuana at this time,” the agency said in a statement. The EPA has not demanded proposals from states that have legalized marijuana use.

Some states, meanwhile, have published pesticide rules — well after they’d legalized cannabis use. Colorado, Washington and Oregon have issued lists of pesticides they say are safe to use; others are still being tested.

In mid-February, Colorado piggybacked on its recalls — which were initiated by the city of Denver, rather than the state — by placing a hold on the sale of products made by two marijuana cultivation sites in Colorado Springs it said used pesticides containing myclobutanil pending an investigation. The companies, Dr. Releaf Inc. and High Mountain Medz, did not respond to requests for comment.

The holds were the first actions taken under a November order issued by Governor John Hickenlooper that declared it a public health risk to use pesticides not approved by the state.

Oregon, meanwhile, stopped the sale of the previously approved pesticide Guardian in February after Voelker discovered that the label did not disclose the active ingredient, abamectin — which wasn’t approved for cannabis use — in lab testing and alerted state officials. Guardian manufacturer All In Enterprises declined to comment.

Oregon has approved about 250 pesticides for use on cannabis: It allows pesticides that can safely be used in unlimited amounts on edible products and adopted its tobacco-growing rules for smokable marijuana. The state is working with the EPA, Washington and Colorado to refine regulations and develop a testing program, according to Sunny Jones, the Oregon Agriculture Department’s cannabis policy director.

Washington issued pesticide guidelines for recreational marijuana as part of its July 2014 adult-use legalization rollout. It currently has no separate pesticide guidance for medical marijuana, which was legalized in 1998, but the recreational guidelines will extend to medical cannabis in July.

The state in December issued its first and only administrative holds on New Leaf Enterprises and BMF Washington, which both grow marijuana and make products from it, saying pesticides not approved for recreational production were in their plants. The hold on New Leaf ended in January, according to a state spokesman, while BMF’s continues.

New Leaf founder Boris Gorodnitsky said the pesticides were traces from a previous medical grow. Once discovered, the company conducted an internal investigation and stopped using plants that contained the chemicals.

The hold was a “nightmare” for New Leaf, according to Gorodnitsky, who said lost business required the company to lay off most of its staff. BMF, which is still under the hold, said it is working with the state “to better understand the levels of pesticides on the products.”

The combination of marijuana’s federal illegal status and varied state pesticide regulations creates complications for companies like New Leaf, according to Gorodnitsky. The goal for regulators, he said, should be to reduce harm for consumers, rather than prohibiting pesticide use.

“The reason it’s such a mess is not because it’s unsafe. It’s because [cultivation] is not federally regulated,” he said.

Nevada waited 15 years after legalizing medical marijuana use to allow sales in dispensaries — which began in July — while it addressed questions about pesticides and other concerns. The state allows cultivators to use 22 pesticides on medical marijuana crops in low levels. Crops are tested by independent labs before they are approved for sale; they are destroyed if unapproved pesticides are found.

While the delays have slowed the growth of businesses hoping for quick profits, some say they’ve put companies in the state on a firmer footing.

“Cultivators want to know what the rules are and want to play by the rules,” says Todd Denkin, chief executive at Las Vegas-based cannabis testing service Digipath Labs. “If you can’t grow a clean product, you’re going to be out of business.”

‘Everyone is willing to do what it takes’

As state governments wrestle with pesticide regulation, some people have taken matters into their own hands.

In October, a recreational cannabis customer joined a medical cannabis customer to file a class-action suit against Denver-based marijuana edible manufacturer LivWell, claiming financial damage because the company didn’t disclose that it used myclobutanil.

The suit was dismissed in February after the Denver District Court ruled that the suit failed to prove injury or damage. Corry & Associates attorney Rob Corry, one of the lawyers who brought the suit, said he is still considering whether to appeal or amend the complaint.

LivWell said it stopped using myclobutanil in early 2015, before regulatory issues arose. “None of our products have ever been recalled, and we have never received a health-related complaint regarding our products,” said LivWell Chief Legal Strategist Dean Heizer. “The lawsuit has not impacted our business.”

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And after Oregon stopped the sale of Guardian, a customer sued its manufacturer, All In Enterprises, in February, alleging deceptive practices in marketing the product as “100% natural” and failing to disclose its active chemical ingredient. The class-action suit wants financial relief for people who wouldn’t have bought it if they’d known what was in it.

While lawsuits like these can hurt companies’ brands and sales, some experts view them as bumps in the road to productive long-term regulation. The industry hasn’t experienced “dramatic, law-changing events” yet, according to Hilary Bricken, an attorney at Seattle-based marijuana industry law firm Canna Law Group, “but it’s brewing.”

Cannabis products for sale at a dispensary in Denver on Jan. 1, 2014, the day legal recreational marijuana sales went into effect. Getty Images

More broadly, some see complications related to pesticides as normal for a young industry. “This is nothing new,” says Trek Hollnagel, a member of cannabis industry and lifestyle news publication DOPE Magazine’s board of directors. “The willingness of the cannabis community to put reforms in place is beyond compare. Everyone is willing to do what it takes to make this industry succeed.”

Still, a concern that pesticides could upset the detente between the industry and the federal government lingers.

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“We have an incubated environment we’re allowed to operate in right now,” said Derek Peterson, chief executive of cannabis-focused agriculture company Terra Tech. “If we keep opening up opportunities for people to use dangerous things on plants, it becomes an embarrassment and we invite more scrutiny from the federal government. It would be a huge step backward.”

This article was first published on March 4, 2016.