The total contents of Escherichia coli, enterococci, Clostridium perfringens and sulphite reducing clostridia, as well as the presence of Salmonella, Campylobacter, Shiga-toxigenic E. coli (STEC), Listeria monocytogenes, Mycobacterium, astroviruses, caliciviruses, Cryptosporidium and Giardia, were analysed in raw sewage sludge samples taken at 22 sewage water treatment plants, in peat-sludge mixtures, in stabilised (using quicklime, anaerobic mesophilic digestion or in-vessel composting) sludge, and in sludge composts of different ages.

Raw sewage sludge, poorly treated lime-stabilised sludge, digested sludge and sludge-peat mixtures contain a wide variety of potential human and animal pathogens, and thus their use in agriculture is not recommended. It is also recommended that digested sludge and sludge sanitated in in-vessel composting plants should be further composted or cured in open-air windrows or mattresses, with adequate turnings, for at least six months.