By Danni Sinnett and Issy Bray
Across Europe there is a vast legacy of contaminated sites from past industrial, commercial and military activity, waste disposal, mineral extraction and other uses. WHO Europe published a report examining the Urban redevelopment of contaminated sites, which summarises the findings from an expert discussion which considered a review of the evidence on environmental and health impacts of remediation, a suite of European redevelopment case studies and a reflection on the applicability of impact assessment tools during remediation and redevelopment processes.
This blog focuses on the findings from our evidence review commissioned by WHO Europe. The review sought to answer the question: to what extent does the remediation and subsequent redevelopment of contaminated sites reduce environmental and health risks to new and existing populations and ecological systems, and are there any effects on equity in terms of the distribution of risks and outcomes or the identification of disadvantaged groups either pre- or post-remediation?
A search strategy was developed that brought together three sets of terms related to: the contaminants (e.g. lead, polyaromatic hydrocarbons) and land uses (e.g. mining, industrial); remediation and redevelopment; and the outcomes related to health (e.g. mortality, cancer). A search of standard academic databases resulted in 6903 papers. The titles and abstracts of these were then screened based on whether they reported changes in outcomes related to the environment or human health, in either new or existing populations, as a result of the remediation and, where possible, subsequent redevelopment of contaminated sites.
The vast majority of studies report soil and water concentrations, outcomes related to ecotoxicological or human health, or risk assessments pre-remediation, the findings from laboratory or field-scale experiments testing the efficacy of remediation technologies, the results of studies that model exposure or provide commentaries or reviews of remediation technologies. This meant that only 50 papers met the criteria for full-text screening.
In total sixteen papers based on outcomes related to health were taken forward to evidence synthesis:
- Three studies that examine the outcomes related to the health of new residents following remediation and redevelopment of contaminated sites;
- Nine studies that examine the outcomes related to the health of children in existing neighbourhoods previously exposed to lead (n=8) and chromium (n=1) following remediation and public health campaigns to reduce exposure (e.g. by removing hand to mouth behaviour in children, improved hygiene and home cleaning);
- Four studies that examine the outcomes related to the health in existing populations following remediation of contaminated sites.
Most of these studies were set in the United Sites and focused on reductions in blood lead concentrations in children, following a combination of soil remediation and/or public health campaigns to reduce exposure. Two further studies examined the impacts of remediation on soil contaminated with chromium and sediments contaminated with polychlorinated biphenyls (PCBs). Some studies suggest that soil cover alone is not sufficient without an excavation of contaminated surface soils to prevent upward migration, and area-wide remediation is required to prevent recontamination of residential gardens. Although it appears that soil remediation is largely responsible for the declines in soil, water, dust and blood concentrations, there is also consistent evidence that public health campaigns are effective at reducing exposure pathways where existing populations are present.
The evidence suggests that remediation via removal, capping, and replacing soil, with planting vegetation on bare soils is effective at reducing concentrations of lead and chromium in blood and urine in children, although this approach to remediation is not considered sustainable. Very few of the studies explicitly considered equity in their study design or reporting of outcomes, despite it being widely reported in the environmental justice literature that disadvantaged groups are more likely to live near contaminated sites.
The review considered a further 31 studies related to environmental outcomes following full-scale remediation and/or redevelopment of contaminated sites. Eighteen studies examined various environmental outcomes following remediation of inorganic contaminants, including metals and metalloids, and asbestos, mainly through removal and/or capping of soil and thirteen studies examined the environmental outcomes following remediation of organic contaminants including pesticides, PCBs, total petroleum hydrocarbons and polyaromatic hydrocarbons.
The nature of research and development of remediation methods for contaminated land mean that there are very few studies in the academic literature that report on the outcomes related to human and environmental health following full scale remediation. Instead, the literature focuses on laboratory and pilot studies, with the results of long-term monitoring programmes tending to not be available in the public domain. In addition, the report summarises other limitations in the evidence and provides recommendations to improve the quality of evidence.
Overall, the review found that there is consistent evidence that, when best practice is employed, remediation of contaminated soils is effective at reducing both direct and indirect exposure to pollution in nearby populations and for reducing environmental risk.