WASHINGTON — Federal health officials have agreed to investigate whether Maine soldiers were exposed to potentially toxic herbicides – including Agent Orange – while training at a Canadian base during the mid-1950s to the mid-1980s.

In a letter to Sen. Susan Collins, R-Maine, the director of the Centers for Disease Control and Prevention pledged to “conduct a thorough investigation of the situation” at the Canadian Forces Base Gagetown in New Brunswick, where herbicides and defoliants have been used for decades.

Dr. Thomas Frieden, director of the CDC, said staff have requested documents and reports to look into the possibility that Maine veterans were exposed to harmful chemicals.

“The Centers for Disease Control and Prevention (CDC) and the Agency for Toxic Substances and Disease Registry (ATSDR) share your concerns about the health of our military veterans and this situation in particular,” Frieden wrote.

Frieden was responding to a June 2012 letter from Collins in which the senator urged the ATSDR to conduct a detailed analysis of the potential health risks for Mainers who trained in Gagetown.

Although Agent Orange – a Vietnam War-era defoliant that causes cancer and severe health problems – was only used for several days at Gagetown in the 1960s, the base continued to use other herbicides and defoliants that have been linked to health problems.

Concerns over troop exposure to potentially toxic herbicides at the Gagetown base are not new. The Canadian government investigated the issue years ago and subsequently agreed to compensate some soldiers who were sickened due to exposure to Agent Orange. Maine officials have also been involved in the issue since at least 2005.

For instance, in an August 2006 “information paper” on the issue, the Maine Department of Defense, Veterans and Emergency Management expressed concerns about the “bigger issue” of Maine National Guard troops’ exposure to herbicides other than Agent Orange that were used for decades.

Although those chemicals were approved for use as herbicides by Canadian government, that fact does not negate the reality that the nature of military training could increase the risk of exposure, the paper’s authors wrote.

“Maine National Guard soldiers dug foxholes, low crawled, slept in pup tents, and lived in some of these areas for up to 12 days at a time,” the paper stated. “Guard engineers graded roads where herbicides were used to keep brush growth down on the edge of the road; cleared brush out of and constructed bivouac sites; and conducted demolition and engineer missions all over CFB Gagetown. Artillerymen fired thousands of rounds into the impact areas and the detonation of those rounds put those chemicals back into the air to be dispersed wherever the wind took them.”

Collins said today she was pleased with the CDC’s decision to look into the matter.

“Protecting the health of those who were training to protect us is a solemn responsibility from which we must not walk away,” Collins said in a statement.