For many experts, Health Secretary Robert F. Kennedy Jr. ’s promise for “pulling back the curtain” to find autism’s causes in a few months is jarring — and unrealistic.

Health and Human Services Secretary Robert F. Kennedy Jr. celebrated Mother’s Day with his family by swimming in a contaminated Washington, D.C., creek used for sewer runoff. “Mother’s Day hike in Dumbarton Oaks Park with Amaryllis,