Violent explosions, deadly truck fires and devastated small businesses may have stemmed from environmental regulations based on a flawed study; one led by researchers accused of faking their credentials and ignoring serious conflicts of interest.

Special filters intended to decrease emissions by diesel trucks of particulate matter 2.5 are required by the California Air Resources Board to be equipped on all diesel trucks that operate in California. If the filters are judged to be successful in decreasing air pollution, some observers worry that the U.S. Environmental Protection Agency will encourage more states to mandate their use.

Such encouragement from EPA would come despite litigation charging that the filters endanger drivers and others with extremely high-temperature fires, significant economic losses, and doubts about the device's effectiveness in reducing harmful emssions.

The crucial research that formed the basis for the regulation mandating use of the filters was led by Hien Tran, who faked his Ph.D. credentials, a fact initially kept from board members by CARB Chairman Mary Nichols. Nichols is a former senior federal environmental executive.

After Tran was exposed, Nichols ordered a reassessment of his findings. However, the follow-up study used non-peer-reviewed research that a federal review panel called "questionable," according to a 2014 report prepared by minority members of the Senate Environment and Public Works Committee.

Also, the original study that claimed to determine the danger of the specific particulate matter was conducted by a panel of independent researchers led by John Froines, who later resigned as a result of an official investigation of his conflicts of interest.

Observers wonder why the regulation was adopted despite problems the underlying research.

"California, for whatever reason, has decided that they can pass whatever regulations they want," said owner of Old Durham Wood, a trucking company, Randy McLaughlin.

Older trucks, which will eventually be banned from operating anywhere in the state unless equipped with the filter, must have filters installed, while engines built after 2009 nationwide come with a device as standard equipment.By 2023, only engines from 2010 and on will be allowed to operate on California roads and highways.

Because of problems with both types of filters, the Alliance for California Business, which represents small businesses in the Golden State, filed suit against the board.

"The filters were not evaluated for their safety," said alliance representative Therese Cannata. "As safety problems emerged, the board, in my opinion, has turned a blind eye."

"The alliance is asking for a moratorium on the filters until after their safety is proven," she continued. "The regulatory agency has to admit that they made a mistake and moved too fast."

The alliance claims the filters increased the frequency and intensity of truck fires. If a disturbance, such as a minor accident, causes diesel to spill onto a filter — which can heat up to 1,400 degrees — a fire could erupt, made especially dangerous by extra pressure and oxygen created by the device.

"You're creating a torch in your engine," Cannata said.

"We want the filters to be safe," said alliance president and trucking business owner Bud Caldwell. "I am scared of hauling diesel fuel."

However, the filters must meet safety requirements, according to the California board. The alliance claims board officials have been unable to support their safety claims for the filter.

"It's become a finger-pointing game between installer, manufacturer, and the board," Caldwell said.

"We have been tracking fires on trucks for over 18 months," Cannata said. "What we see is a rise in fires that are very different from before these devices were on the road."

The alliance cited a fire caused by a filter manufactured by Cleaire Advanced Emission Controls that burned 5,300 acres of Washington state forest in September 2011. Though the California board wrote a letter to the manufacturer nine days later, a formal recall was not issued until the following year.

"We're going to ask people from the California board to come under oath and tell us what we know," Cannata said. "I believe that the board officials are not going to come out and say the devices are safe. I don't think that they're going to say that they've studied it."

The board declined to comment on pending litigation. Cannata also said the alliance submitted 22 legal declarations, while the board offered none.

The alliance additionally claimed that the filters are highly expensive, with initial costs ranging from $18,000 to $20,000.

"A lot of small, family-owned businesses have to go into debt to afford a device that causes trucks to go down frequently," Cannata said.

"The air resources board conducted a thorough economic analysis when developing the Truck and Bus Regulation," board spokesman Karen Caesar said. "That analysis was reviewed by the board before making a decision to adopt the rule."

Caesar also said the board invested more than $640 million to help retrofit or replace trucks, though the alliance argued that amount has been exaggerated and was not distributed evenly across the state.

However, because the devices allegedly restrict the engine's ability to breathe, truckers still face expensive repairs and consequential lost revenue while their vehicles are in the shop.

"There are 50,000 retrofits in operation in California," said Caesar. "Each of these retrofits was verified through a robust process managed by the board to ensure the filters work as designed."

Non-compliant trucks can be fined up to $1,000 per violation per day as of January, though a board official said they typically only enforce the fine once per month.

Regardless of the alleged danger and price, the alliance also cited a board-funded study that questions the filters' efficiency in destroying pollution.

Essentially, the device's extreme heat burns off the dangerous pollutants. However, the study found that the resulting emissions contain a smaller version of the same dangerous particles.

Caesar did not comment directly on the study.

"Emissions from regeneration are much lower than the emissions that would have occurred had a [filter] not been in place, reducing emissions from the diesel engine," she said. "Diesel particulate filters have been demonstrated to provide a 98 percent reduction in particulate-matter mass which has been shown to provide substantial health and air quality benefits."