Ships of the desert. Camels were domesticated more than 3,000 years ago, and to this day, humans depend on them for transport across arid environments. They can easily carry an extra 200 pounds (90 kilograms) while walking 20 miles (32 kilometers) a day in the harsh desert.
Definition - What does Permissible Exposure Limit (PEL) mean? Permissible exposure limit (PEL) is the legal limit in the U.S. for maximum concentration of any chemical in the air to which a worker may be exposed continuously for eight hours without any danger to health and safety. PEL is established by the Occupational Safety and Health Administration (OSHA).
The maximum permissible exposure for a person under 18 working with radiation is one-tenth the adult limit or not to exceed 500 millirems per year above the 300+ millirems of natural sources, plus medical radiation.