Within a worker thread, worker.getEnvironmentData() returns a clone of data passed to the spawning thread's worker.setEnvironmentData(). Every new Worker receives its own copy of the environment data automatically.
import {
Worker,
isMainThread,
setEnvironmentData,
getEnvironmentData,
} from 'node:worker_threads';
if (isMainThread) {
setEnvironmentData('Hello', 'World!');
const worker = new Worker(__filename);
} else {
console.log(getEnvironmentData('Hello')); // Prints 'World!'.
}