Implement IAM policies within the Lambda console to restrict access to the environment variables.

Employ AWS Step Functions to manage the environment variables, granting runtime access with IAM permissions limited to the necessary Lambda functions.

Utilize AWS Secrets Manager to store the environment variables, ensuring runtime access with IAM permissions that are restricted to the required Lambda functions.

Leverage AWS Systems Manager Parameter Store to store the environment variables as secure string parameters, providing runtime access with IAM permissions limited to the necessary Lambda functions.