The story of phosphorus: Global food security and food for thought

Food production requires application of fertilizers containing phosphorus, nitrogen and potassium on agricultural fields in order to sustain crop yields. However modern agriculture is dependent on phosphorus derived from phosphate rock, which is a non-renewable resource and current global reserves may be depleted in 50-100 years. While phosphorus demand is projected to increase, the expected global peak in phosphorus production is predicted to occur around 2030. The exact timing of peak phosphorus production might be disputed, however it is widely acknowledged within the fertilizer industry that the quality of remaining phosphate rock is decreasing and production costs are increasing. Yet future access to phosphorus receives little or no international attention. This paper puts forward the case for including long-term phosphorus scarcity on the priority agenda for global food security. Opportunities for recovering phosphorus and reducing demand are also addressed together with institutional challenges. © 2009

A spatial analysis of pit latrine density and groundwater source contamination

This study aims to assess the relationship between chemical and microbial contamination of groundwater sources and a range of potential hazards in two peri-urban areas of Kisumu, Kenya where shallow wells and pit latrines are widely used. From 1998-2004, 263 samples were taken from 61 groundwater sources and tested for thermotolerant coliforms. 18 of these sources were also tested for chemical contaminants, including nitrate, chloride and fluoride. The locations of all water sources, buildings, and pit latrines in the study area were surveyed. Local pit latrine densities were calculated using a Geographic Information System (GIS). 10 out 18 samples were above World Health Organization guideline values for nitrate, 236 out of 263 were positive for thermotolerant coliforms, and all were above guideline values for fluoride. There was no relationship between thermotolerant coliform levels and daily rainfall patterns, nor with sanitary risk inspection scores for samples from shallow wells (r=0.01, p=0.91, n=191). The density of pit latrines within a 100 metre radius was significantly correlated with nitrate and chloride levels (r=0.64, p=0.004 and r=0.46, p=0.05 respectively) but not with TTC (r=0.22, p=0.11). These results illustrate both the public health risks associated with shallow groundwater sources, onsite sanitation, and high population density. These findings have implications for current policies that promote latrine construction, especially in peri-urban areas of high population density. More comprehensive studies of larger communities should be commissioned to extend this analysis of the links between latrine density and groundwater contamination and so identify the contingent policy risks

Household drinking water in developing countries: a systematic review of microbiological contamination between source and point-of-use

Summary Objective To assess the extent and causes of microbiological contamination of household drinking water between source and point-of-use in developing countries. Methods A systematic meta-analysis of 57 studies measuring bacteria counts for source water and stored water in the home to assess how contamination varied between settings. Results The bacteriological quality of drinking water significantly declines after collection in many settings. The extent of contamination after water collection varies considerably between settings, but is proportionately greater where faecal and total coliform counts in source water are low. Conclusions Policies that aim to improve water quality through source improvements may be compromised by post-collection contamination. Safer household water storage and treatment is recommended to prevent this, together with point-of-use water quality monitoring