The nation’s most-stringent state law to protect personal health data begins to take effect on March 31, affecting countless companies that do business in Washington state.

The state’s My Health My Data Act is loaded with potential data traps for companies that collect, process, share or sell consumer health data, even the kind of data that may not explicitly appear to be so specific as to be relevant. Companies that haven’t regarded themselves as keepers of health data may be implicated.