DNA contamination minimisation - finding an effective cleaning method

Recent environmental monitoring studies have highlighted a need to confirm cleaning procedures are performing to suitable levels for highly sensitive STR kits such as PowerPlex 21. To ensure that DNA contamination minimisation procedures are adequate, we have investigated the efficacy of sodium hypochlorite and a commercial, non-corrosive alternative, Virkon, at a range of concentrations for their DNA decontamination ability. Cleaning solutions were trialled across a range of body fluids and surface types, to cover the variety of potential contamination circumstances encountered within typical forensic laboratories. Given all factors tested, it was concluded that a 1% solution of sodium hypochlorite, sprayed on the surface and left for 5 min before drying and wiping with 70% ethanol, was able to remove DNA, saliva, blood, semen and skin cells from both smooth and pitted surfaces. However, safety testing revealed that the combination of hypochlorite and ethanol produced levels of gaseous chlorine at or above the recommended exposure limits. Subsequently, a cleaning protocol of 1% hypochlorite followed by distilled water was tested for efficacy, and subsequently introduced throughout the laboratory.