Soil and human health: an epidemiological review

Abstract

Two different approaches have been used to study relationships between soil and human health: aggregateand individual-level. Aggregate-level is the primary approach used in the geosciences and broadly relates spatial soil characteristics to geographic incidence of disease. However, this may not be appropriate for a wide range of exposures and disease outcomes. For example, many diseases with long latency periods are associated with early life or cumulative exposure to the causative agent, rather than an individual's current geographical location. Public health scientists and epidemiologists often refer to aggregate-level studies as being 'hypothesis forming', and consider individual-level approaches as the 'gold standard' for investigating causes of human health outcomes. This paper investigates the appropriateness of individual-level study for disease outcomes associated with soil by reviewing the weight of evidence from individual-level studies that have included exposure to soil as a risk-factor for disease. The majority of these studies are very specific, inspired by explicit case reports and medical records. The review showed that exposure to soil was implicated mainly in the spread of enteric parasites, but also in the incidence of certain cancers, bacterial infections, and mycoses. There was little evidence for specific soil contaminants as causative agents of disease at an individual level but there was also little evidence contrary to this. Further individual-level studies into soil:human health scenarios are required in order to derive more appropriate dose-effect relationships for regulatory science and risk assessment.

Risk factors forToxoplasmainfection in pregnant women in FYR of Macedonia

“…Of the socio-demographic and transmission risk factors examined as potential risk factors for Toxoplasma infection, exposure to soil has been determined as the single predictor of Toxoplasma infection. The significance of exposure to soil as a risk factor for Toxoplasma infection is well-known (Hall et al, 2001;Hough, 2007), and it raises the issue of the significance of cats as an infection source; since, however, this study did not show pet cat ownership to be a risk factor, environmental contamination with oocysts by the stray cat population should be considered. It must be noted, however, that this analysis of risk factors may be limited by the type of study itself, which although generally used, is less accurate than a case-control study, and also, by the broadness of the questionnaire.…”

The past, present, and future of soils and human health studies

“…A number of articles have been published over the last 10 years reviewing the status of our knowledge of soils and human health (e.g., Deckers and Steinnes, 2004;Hough, 2007;Brevik, 2009aBrevik, , 2013aPepper et al, 2009;Handschumacher and Schwartz, 2010;Steinnes, 2011;Pepper, 2013). Books addressing soils and human health are also being published.…”

Bioavailability: Exposure, Dose and Risk Assessment

“…These measurements can then be combined with information about the activity budgets of the individuals. Usually, when risk is being estimated from the perspective of the causative agent, the activity budgets (and corresponding inhalation rates) used are theoretical [4,40]. However, for a population-specific health study directed from the perspective of the outcome, it may be beneficial to construct activity budgets for subsets of the population.…”

“…Studies looking at exposures that are of more relevance to environmental regulation are confined to a small number of environmental epidemiology and exposure biomarker studies that cover a limited number of trace elements from an even more limited range of exposure scenarios. Certainly, the number of environmental epidemiology studies examining health outcomes associated with exposure to soil is surprisingly small [4]. Out of these, only a few studies consider specific trace elements [4].…”

“…Certainly, the number of environmental epidemiology studies examining health outcomes associated with exposure to soil is surprisingly small [4]. Out of these, only a few studies consider specific trace elements [4].…”