 The absorbed energy can result in defects including pyrimidine dimers.These dimers can prevent replication or can prevent the expression of necessary proteins, resulting in the death or inactivation of the organism.10.1007/978-3-642-01999-9, Ultraviolet Germicidal Irradiation Handbook, Kowalski 2009

This process is similar to the effect of longer wavelengths (UV-B) producing sunburn in humans.