The Environmental Protection Agency is moving forward with a vaguely worded proposal that may lay the groundwork to zap current federal regulations on low-dose radiation exposures.

Today, Wednesday, October 3, the Senate Committee on Environment and Public Works is holding a hearing to discuss the proposed rule, titled Strengthening Transparency in Regulatory Science (PDF), which the agency first introduced in April.

Though the proposed rule does not explicitly mention radiation exposure regulations, a press release from the agency announcing the proposal makes clearer the agency’s intentions, the Associated Press first reported. The release quotes toxicologist Edward Calabrese of the University of Massachusetts, saying:

“The proposal represents a major scientific step forward by recognizing the widespread occurrence of non-linear dose responses in toxicology and epidemiology for chemicals and radiation and the need to incorporate such data in the risk assessment process.”

Calabrese is the lead witness in today’s Senate hearing on the EPA’s proposal. Though his early research focused on pollutants, he is best known as a long-standing critic of the widely accepted methods for modeling cancer-causing effects of radiation exposure. Specifically, he has railed against the federal agency’s reliance on the linear nonthreshold (LNT) model, which essentially backs the idea that there’s no safe or risk-free level of radiation exposure.

Instead, Calabrese is a strong proponent of the notion of hormesis, which suggests that some toxic substances have a biphasic dose response—they can be beneficial at low doses and toxic at higher doses. A common example used by proponents is sunlight, which aids in the synthesis of Vitamin D but can also cause DNA damage leading to cancer. Calabrese argues that hormesis applies to low-dose radiation exposures, which may be encountered at places such as nuclear facilities, oil and gas operations, medical centers with imaging equipment, and Superfund sites.

Calabrese’s take is heavily contested. The National Research Council and the National Council on Radiation Protection and Measurements (NCRP) both continue to support using LNT for radiation protection and exposure modeling. In fact, the NCRP just this year doubled-down on its support of the model. It conducted a review of epidemiological studies on cancer rates in people exposed to low doses of radiation and concluded:

[T]he available epidemiologic data were broadly supportive of the LNT model and that at this time no alternative dose-response relationship appears more pragmatic or prudent for radiation protection purposes.

The Environmental Protection Agency appears to be moving forward with Calabrese’s take on things, however. The AP reports that an EPA website on guidelines for radiation effects read as recently as March that: “Current science suggests there is some cancer risk from any exposure to radiation.”

Whereas, now the site has been edited to read: “According to radiation safety experts, radiation exposures of 5–10 rem (5,000–10,000 millirem or 50–100 millisieverts) usually result in no harmful health effects, because radiation below these levels is a minor contributor to our overall cancer risk.”

In a 2016 interview with The Breakthrough Institute, a California-based think tank, Calabrese laid out his vision for what such a regulatory shift could mean, saying:

Getting rid of regulations based on the LNT theory would result in an increase in the acceptable dosage by at least several hundred fold. And that would have a huge impact. This would have a positive effect on human health as well as save billions and billions and billions of dollars. The regulatory agencies are kind of a cult, but they don’t know they’re part of a cult.

Other supporters of hormetics and critics of current regulations are applauding the changes that seem to be underway. Brant Ulsh, a physicist with the California-based consulting firm M.H. Chew and Associates, told the AP that “right now we spend an enormous effort trying to minimize low doses… Instead, let’s spend the resources on minimizing the effect of a really big event.”