Colorado’s U.S. Sen. Michael Bennet has written to the Trump Administration in protest of its decision to exclude several health conditions from automatic veterans benefits despite a link to a well-known Vietnam War-era chemical.

“The Office of Management and Budget’s (OMB) decision to exclude bladder cancer, hypertension, Parkinsonism and hypothyroidism as diseases linked to Agent Orange is frustrating and unfair,” said the letter dated Nov. 27.

U.S. Sen. Robert Casey, D-Pa., also signed on.

The previous Trump-appointed secretary of veterans affairs, David Shulkin, agreed to include three of those four conditions, but Military Times reported that the White House blocked him from doing so.

A 2016 report from the National Academies of Medicine found there is “sufficient” evidence to link hypertension to Agent Orange, and “limited” evidence for the other conditions.

Bennet and Casey asserted that the exclusion would affect 83,000 veterans.

The military used Agent Orange from 1962 to 1975, spraying millions of gallons to remove tree cover and destroy crops. The American Cancer Society reports that veterans could have gained exposure by breathing, ingesting or absorbing the chemical through their skin. There is sufficient evidence of an association between Agent Orange exposure and soft tissue sarcoma, non-Hodgkin lymphoma, Hodgkin lymphoma and chronic lymphocytic leukemia, according to the organization.

In addition to U.S. service members, an estimated three million Vietnamese are also suffering from diseases associated with their exposure.