the recycling of cardboard boxes helps to keep them clear of bacterial contamination, a study has found.commissioned by the us organisation corrugated packaging alliance, and carried out by university of california davis and haley & aldrich, the study found that 100 of boxes tested met acceptable levels of bacteria for food packaging.with no guidelines on packaging bacteria levels existing from the us food and drug administration, a 1000 colony forming units per swab threshold was used by the study that had been developed by the university of guelph, food safety authority of ireland,