DNA damage and repair proteins in cellular response to sulfur mustard in Iranian veterans more than two decades after exposure.

•Even more than two decades after exposure to SM, there is still evidences of DNA damage as well as impaired repair mechanisms in cells of exposed individuals.•Mean levels of XPA, MRE11, RAD51 and NBS1 were lower in SM-exposed patients and the decrease in NBS1 was significant.•Even though the raised level of phosphor-H2AX in SM-poisoned group compared to the controls was not significant it was consistent with DNA damage findings.•There were correlations between the values of RAD51 and NBS1 proteins as well as XPA and MRE11 proteins. However, none had significant correlation with years passed after exposure.