Elnahal said that he is optimistic that the VA will succeed in the effort, given that the veterans already are enrolled in care and the department has at least some contact information for them.

He hopes the effort will encourage the veterans to turn to the "VA for their health care more regularly," he added.

"I hope that when they come into our brick-and-mortar institutions or otherwise get screened, they realize that we've got a team and set of teams across the country dedicated to veteran care," Elnahal said during a press call with reporters Nov. 20.

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The exposure screening process consists of a medical provider asking a patient a set of questions. Those include whether the patient thinks they were exposed to any toxic substances from burn pits, Agent Orange, radiation, contaminated water or other pollutants; what they think they may have been exposed to; and whether they have questions.

The screenings are to be conducted at least every five years, with the results kept in the veterans' health records, according to the VA.

Elnahal said that if a veteran has concerns about an exposure or a clinician believes the patient may have a condition related to an exposure, they will be "referred for further care."

He could not provide information on whether the screenings have sparked any immediate specialty care referrals and if so, what type of care.

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But, Elnahal added, VA physicians are trained to understand the veterans' responses and the potential health effects of hazardous materials exposure.

According to the department, 97% of its clinicians have completed PACT Act clinical training from the VA's War-Related Illness and Injury Study Center, which is a module for assessing deployment-related environmental exposures.

"That's been a key part of what we do so that no clinician can be surprised or should be surprised when a veteran presents with a concern about an exposure and how that might relate to their health," Elnahal said during the press call.

The PACT Act broadened health care services, disability compensation and benefits for an estimated 5 to 6 million veterans who served overseas during the post-9/11 wars, the first Persian Gulf War and the Vietnam War.

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The toxic exposure screenings are aimed at those at risk for illness as a result of exposure to burn pits, airborne particulate matter, chemicals such as Agent Orange, toxic water at Camp Lejeune in North Carolina and elsewhere, and other environmental pollutants.

Elnahal said that the VA will make every effort to screen all its patients but, ultimately, it's the veterans' decision.

"The law requires us to screen them ... which is an extensive outreach effort on top of the screening effort," Elnahal said. "Obviously, it's the veterans' choice at the end of the day and whether they want to."