Dorany Pineda / Associated Press

Coupled with exertion, extreme heat exposes agricultural workers to more health risks, including miscarriages, stillbirths, preterm births and low birth weight in infants.

Federal agents have rounded up dozens of California farmworkers in large-scale raids at packinghouses and fields that farm bureaus say threaten businesses that supply much of the country’s food. Community advocates said several dozen immigrants were arrested after agents raided packing sheds and fields. Many of the arrests took place on farms northwest of Los Angeles.