A delivery in Wilmington, N.C., this month. Heat is linked to hundreds of workplace deaths each year, but labor groups say the true toll is unknown because heat-related illnesses are not properly tracked or reported.

Loading sugar cane to transport it to mills in the Satara district of India’s Maharashtra State in March last year. Laborers often work in couples, paid through contractors.

Hansa Ahir, left, who salvages recyclable waste for a living in Ahmedabad, India, bought an insurance policy to cover her income on days when heat makes it dangerous to work.