Ngo Sy Loi, a Vietnam War veteran, takes out one of his military models at his house in Bac Ninh, Vietnam, on May 25. (Linh Pham/Getty Images)

President Obama is right to reach across the Pacific Ocean to reinforce relations with Vietnam [“Three kept from meeting Obama,” news, May 25]. However, if we are serious in our commitment to our new ally, we must recognize and fix the legacy of war that we left behind more than 40 years ago.

Dioxins and related compounds that were sprayed during the defoliation of large portions of southern and central Vietnam are still present in soil and waterways of the country’s forest and agricultural areas. Millions of children and adults were affected and still suffer because of disabling birth defects, even two generations later. Vietnamese scientists, U.S. academics (including me) and others in health organizations have pointed to the eroding landscapes and toxic legacy of the “American War” in Vietnam. But the U.S. government and the herbicide manufacturers have so far avoided taking responsibility, instead focusing on cleanup of a few airbase “hot spots.”

If the United States wants to use Vietnam to poke at China, as that country fears, we should at least clean up the first mess we left behind.

Fraser Shilling, Davis, Calif.