Assessing potential risk of heavy metal exposure from consumption of home-produced vegetables by urban populations.

Abstract

We performed a risk assessment of metal exposure to population subgroups living on, and growing food on, urban sites. We modeled uptake of cadmium, copper, nickel, lead, and zinc for a selection of commonly grown allotment and garden vegetables. Generalized linear cross-validation showed that final predictions of Cd, Cu, Ni, and Zn content of food crops were satisfactory, whereas the Pb uptake models were less robust. We used predicted concentrations of metals in the vegetables to assess the risk of exposure to human populations from homegrown food sources. Risks from other exposure pathways (consumption of commercially produced foodstuffs, dust inhalation, and soil ingestion) were also estimated. These models were applied to a geochemical database of an urban conurbation in the West Midlands, United Kingdom. Risk, defined as a "hazard index," was mapped for three population subgroups: average person, highly exposed person, and the highly exposed infant (assumed to be a 2-year-old child). The results showed that food grown on 92% of the urban area presented minimal risk to the average person subgroup. However, more vulnerable population subgroups (highly exposed person and the highly exposed infant) were subject to hazard index values greater than unity. This study highlights the importance of site-specific risk assessment and the "suitable for use" approach to urban redevelopment.

House dust as possible route of environmental exposure to cadmium and lead in the adult general population

“…In case of contamination of the soil by cadmium or lead, consumption of home-grown crops and ingestion of soil particles are well established routes for environmental exposure (Hough et al, 2003). However, a growing body of evidence (Paustenbach et al, 1997) suggests that exposure to soil brought indoors, present as house dust, might also stand for a critical route of exposure.…”

Urban geochemistry: research strategies to assist risk assessment and remediation of brownfield sites in urban areas

“…Metal solubility, depicted as the "free metal ion activity" in the soil pore water was predicted from a pH-dependent Freundlich equation from the total soil metal content, organic carbon content and soil pH (Hough et al, 2004). Published literature (73 studies including Moir, 1992), encompassing 4,500 data points, was then interrogated to derive values for metal concentrations in soils and in vegetable dry matter, together with soil organic matter content and soil pH.…”

“…The potential hazard to the population from the consumption of home grown vegetables has been assessed using the concept of the Hazard Quotient (HQ) (Hough et al, 2004) -the ratio of the average daily dose of the metal (the sum of the total dietary and inhalation exposure and metal in soil and dust ingested) to a reference dose based on the maximum tolerable daily intake that will not result in any deleterious health effects (WHO, 2001). Where the HQ is greater than 1.0, there is a potential risk.…”

Phytoremediation of urban soils contaminated with trace metals using Noccaea caerulescens: comparing non-metallicolous populations to the metallicolous ‘Ganges’ in field trials

“…In contrast with agricultural soils, urban soils are characterized by the spatial heterogeneity of contamination (Alloway 2012;Meuser 2010), which complicates remediation strategies. Urban soil contamination by toxic trace metals is detrimental for soil quality but is also harmful for human health resulting from accidental soil ingestion and consumption of crops grown on these soils, generally more exposed to trace metals than when grown in rural areas (Finster et al 2004;Hough et al 2004;Säumel et al 2012;Wang et al 2005). Conventional soil remediation practices such as excavation are often considered…”