SEATTLE (AP) — A big mound of fresh dirt sits at Terry Taylor's marijuana farm in the high desert of north-central Washington state. Each hole for a new plant gets filled with the clean soil.

Large swaths of recently installed landscape fabric cover the ground, and soon the dirt roads on his property will be covered in crushed rock to keep contaminated dust from covering the crops.

Taylor's pot farm is one of several getting back to business after state regulators halted their operations in April, citing product testing that turned up unacceptable levels of chemicals related to DDT, a synthetic pesticide banned half a century ago.

The affected growers haven't used the pesticide themselves, but they are located on a 5-mile (8-kilometer) stretch of former fruit orchards along the Okanogan River where it was applied heavily and remains in the soil.

The Washington Liquor and Cannabis Board announced last week it had lifted the holds on the businesses, which are now taking steps with state financial support to keep the residual pesticide at bay and rebuild their brands. The board said it will increase pesticide testing for cannabis from the area.

“I haven’t sold any product since April,” said Taylor, who operates two licensed cannabis producer-processors, Okanogan Gold and Kibble Junction. “It’s just destroyed us. No one wants to buy it.”

Taylor, 58, said he’s been living off savings since April. His income has been about one-tenth of what it was previously. He normally has about six full time employees and 20 seasonal workers, but now has only two.

Pesticides in cannabis are a concern for regulators and consumers in legal pot states around the country, especially because the plant is typically smoked or concentrated, a process that can intensify the levels of pesticides in the final product.

Regulators in Vermont early this year pulled pesticide-contaminated pot from five retail stores after a customer reported feeling sick, and Nevada officials issued an advisory about widely available products possibly tainted with an unapproved pesticide.

Due to marijuana’s illegal status under federal law, states have written their own rules about pesticides in cannabis. There is wide variety about which are regulated and how much of a trace can remain in products. It's unclear how many states require cannabis to be tested for legacy pesticides such as DDT.

Washington state's recent experience with DDE, a remnant chemical remaining in the soil as DDT breaks down, suggests such regulations only go so far in protecting public health.

A chemist for the Liquor and Cannabis Board in March noticed several high test results for DDE and traced them to a single growing area. The companies — Okanogan Gold, Bodie Mine, Kibble Junction and Walden Cannabis — immediately issued recalls when asked in April, but by then much of the products had already been sold.

There were 108 samples tested from the companies and 59 came back with unapproved levels of DDE, the board said.

DDT was used heavily in the decades following World War II to control mosquitoes as well as insects that can damage fruit or other crops, but it also killed birds. Rachel Carson’s 1962 book “Silent Spring” documented its effects on nature, which sparked the environmental movement and helped bring about a national ban on the use of DDT in agriculture in 1972.

Studies have shown women with high amounts of DDE in their blood were more likely to give birth prematurely or have a baby with a wheeze, according to the U.S. Centers for Disease Control and Prevention. The chemical is considered a possible carcinogen.

Christopher Simpson, deputy director of the Pacific Northwest Agricultural Safety and Health Center at the University of Washington, said the risk from DDE in cannabis is probably low, though possibly more of a concern for anyone using the marijuana medicinally, since they already may have health issues.

“To my knowledge, nobody has done a really good risk assessment for that,” Simpson said. “You would have to be able to figure out how much cannabis people would consume and how much of that DDT would be deposited in the body. There just isn’t experimental data available.”

Many of the problematic samples of cannabis foliage or oil tested at about 0.2 parts per million, which is above the 0.1 ppm limit in state law but still only about half of what federal authorities tolerate for DDT contamination in tobacco. One sample of cannabis oil or resin came back at 1.7 ppm, the board said.

Given a lack of scientific evidence about what constitutes a dangerous level of DDE in cannabis, Taylor and other affected growers argued that regulators had overreacted by having them halt operations, rather than just issue recalls.

Chandra Wax, director of the board's enforcement and education division, said in a statement that regulators acted “responsibly, swiftly, and intentionally.”

“We recognize the significant impact this had on licensees as well as the risk this posed to the public,” Wax said.

It isn't clear how the DDE wound up in the products. Cannabis is known for its ability to remove contaminants from soil and has been studied for use in environmental cleanup. Taylor said he believed the contamination most likely came from dust settling on the plants as he and others drove or walked on the farm, or even from DDT present in wildfire smoke in the region.

In response to the testing, Washington lawmakers this spring directed $200,000 to help the growers fix their soil, as well as $5 million to study how marijuana plants absorb toxins, how much is transferred to cannabis products and the potential cost to grow plants in pots or broadly clean the soil in the area.

“You want a safe product, obviously, and you don't want people getting sick,” said Republican Rep. Joel Kretz, who represents the area. “I'm hoping we can get it squared away without putting a bunch of farmers out of business.”