The term "dry cleaning" is actually a little misleading. This technique coats clothes in a chemical -- usually perchloroethylene (PERC) -- that tends to be better for cleaning delicate fabrics, such as silk and cashmere, than regular soap and water.
Unfortunately, PERC has been linked to cancer and a number of other health problems. Many cleaners actually send their clothes to dry-cleaning plants, which can release huge amounts of PERC into the earth, air, and water. Workers in these buildings are exposed to toxic chemicals on a daily basis. PERC can also affect customers who regularly dry-clean clothes and bring the toxic chemical into their homes, where it lingers and they breathe it in -- even while not wearing the clothing.
If you must dry clean please remember to remove the plastic bag and hang any dry-cleaned clothes outside (or in a garage) to air out before wearing or hanging in your closet.