Are your hands clean? Pollen retention on the human hand after washing

Pollen retention on clothes, footwear, hair and body has been used to link people to localities with distinctive vegetation, or soils containing distinctive palynomorphs. Little attention has been given to human skin as a possible medium for carrying a forensically important pollen load and whether this might survive attempts to remove it. We report here the results of experiments testing the retention of pollen of 10 flowering plant species on the human skin through repeated cycles of washing and drying hands, using the WHO protocol to standardize hand-washing and drying. Between 0.36% and 2.74% (mean 0.93%) of the initial pollen load was retained through a single hand-wash. Trace amounts of some species survived multiple hand-wash cycles. It is concluded that forensic analyses can be made of the pollen load of those parts of the skin that may have been in contact with palynologically distinctive vegetation, even in cases where the person involved has washed, or been washed. These observations may also be of relevance in cases where human skin became contaminated with other microscopic particulates.