Soap cleans very well in soft water. It is not toxic to water life. It can be broken down by bacteria. However, it is slightly soluble in water, so it is not often used in washing machines. It does not work well in hard water. It cannot be used in strongly acidic solutions. Mild hand soaps are only basic enough to remove unwanted skin oils. For other forms of oil, dishwashing soap is strong enough to remove almost all forms of oil without damaging petroleum products such as plastics. It does not damage skin either.