There are several environmental factors will cause hair loss. From my experience, when I have too much stress, I will get particial hair loss and other physical problems. The other factors are Chemical Exposure and Radiation.
Hot weather can cause hair to become dryer and break off. Also very cold weather can so the same. Saltwater can be very damaging to hair causing split ends and dulling hair color. Sun can effect hair as well. The sun drys out the hair and makes the hair more brittle causing hair loss.