Health Risks Assessment in Three Urban Farms of Paris Region for Different Scenarios of Urban Agricultural Users:A Case of Soil Trace Metals Contamination

Within the context of a worldwide emergence of various forms of urban agriculture, there is a growing awareness concerning the health risks associated to the presence of different pollutants influencing the urban products safety. Among the most common pollutants found in soils and vegetables grown in the city, Trace Metals (TM’s) are of major concern. This paper deals with risks assessment associated with the presence of TM’s in soil, via two main exposure path ways: soil and vegetables ingestions. Risks assessments were conducted for various types of real scenarios encountered in three forms of urban farms near Paris (Ile-de-France Region). The farms have soil TM’s levels in abnormally high concentrations (Pb (Lead), Cd (Cadmium), Hg (Mercury), Cu (Copper) and Zn (Zinc) contents higher than geochemical backgrounds and threshold values for sludge spreading, often used as reference values in France). The results of the Hazard Quotient (HQ)-based risk assessment approach (HQ defined as the ratio of estimated daily intake/tolerable daily intake) show that the most risky scenarios concern urban farmers (HQtot = 1.02, because of the on-site working on a daily basis all year round), children gardeners (HQtot = 1.29) and regular children consumers (HQtot = 1.6 in maximalist scenario, where the consumer would exclusively consume the vegetables of the farm). Next would be the adult gardener scenario (HQtot= 0.9), while the least risky are adult consumer scenarios (HQtot = 0.62) and the farm workers (HQtot = 0.45). For the highest risk scenarios (urban farmers and children), specific and drastic measures may be considered, such as reducing the site frequentation by sensitive populations (child and pregnant women) or proceeding to control analysis of TM’s levels in blood for the most exposed peoples. The choice of parameters used in HQ-based method must be appropriated to the specificities of urban agricultural activities. The uncertainties in the choice of some parameters such as soil ingestion, vegetable intake and exposure frequency could result in an over- or under-estimation of the risk.

Towards a better understanding of pathways of multiple co-occurring erosion processes on global cropland

Soil erosion is a complex process involving multiple natural and anthropic agents,causing the deterio-ration of multiple components comprising soil health.Here,we provide an estimate of the spatial pat-terns of cropland susceptibility to erosion by sheet and rill,gully,wind,tillage,and root crops harvesting and report the co-occurrence of these processes using a multi-model approach.In addition,to give a global overview of potential future changes,we identify the locations where these multiple concurrent soil erosion processes may be expected to intersect with projected dry/wet climate changes by 2070.Of a modelled 1.48 billion hectares(B ha)of global cropland,our results indicate that 0.56 B ha(-36%of the total area)are highly susceptible(classes 4 and 5)to a single erosion process,0.27 B ha(-18%of the total area)to two processes and 0.02 B ha(1.4%of the total area)to three or more processes.An estimated 0.82 B ha of croplands are susceptible to possible increases in water(0.68 B ha)and wind(0.14 B ha)erosion.We contend that the presented set of estimates represents a basis for enhancing our founda-tional knowledge on the geography of soil erosion at the global scale.The generated insight on multiple erosion processes can be a useful starting point for decision-makers working with ex-post and ex-ante policy evaluation of the UN Sustainable Development Goal 15(Life on Land)activities.Scientifically,this work provides the hitherto most comprehensive assessment of soil erosion risks at the global scale,based on state-of-the-art models.