On the other hand, in a study in China, there was no significant relationship between GSTM1 gene deletion NIHL but the results suggested that GSTT1 polymorphism might play an important role in the development of NIHL in Chinese workers and the individuals with the GSTT1 null genotype might be more susceptible to NIHL [15] while in another study on Chinese workers, individuals with the GSTM1 null genotype had a statistically significantly increased risk of NIHL [22]. Here, GSTM1 is linked to noise induced hearing loss.