Can sewerage be considered safe management of human feces?

Although flush toilets and sewerage are usually considered the height of comfort in 21st-century urban societies and the technical and sanitary culmination of human excreta management, they are increasingly being challenged for their environmental footprint and financial cost. Alternative management methods, broadly termed “source separation”, are being developed to address these issues. However, the widely shared belief in the absolute superiority of sewerage for public health is hindering the development of such systems. In this paper, we briefly re-examine the contribution to public health of sewerage as a means of managing human feces, in both its historical development and current implementation. We suggest that management of feces by sewerage is just one element among others in a systemic change, that it usually occurred much later than the others, and that the epidemiological transition usually attributed to sewerage only was, as a matter of fact, strongly supported by associated improvements in drinking water, health care, hygiene practices and good nutrition. We show that risk control in sewered cities is not based on a barrier between human feces and the environment (what we might call sanitation), but on barriers between a contaminated environment and the different uses of water. We call for a more comprehensive analysis of the effects of sewerage on public health, in present times and historically, not only at the scale of a city but at the broader scale of all impacted communities. We also call for a comparison of these effects with those of other sanitation systems that have much lower environmental footprint.