Human Bioaccessibility of Heavy Metals and PAH from Soil

Human Bioaccessibility of Heavy Metals and PAH from Soil

1 Introduction

1.1 Background

Contaminants in Danish soils are regulated according to sets of criteria for maximum contaminant levels (MCLs) before interventions are required. The MCLs are based upon evaluations of acute and chronic toxicity of the contaminants to humans without considering consistently differences in human uptake imposed by different exposure types (e.g.: orally from solution, with food or with soil). During the past 10 years, evidence has emerged that the oral uptake of contaminants may differ widely with the exposure type. In order to evaluate the need for including this new information in MCL setting or enforcement, the DEPA has initiated the present review of the information currently available on variations in human uptake with oral exposure type.

1.2 Scope

The scope of the review is to compile and extract information on bioaccessibility of soil contaminants for human oral exposure emphasising data on bioaccessibility and, if possible, their correlation with soil types, description of processes underlying bioaccessibility variations and finally presentation and evaluation of methods for testing bioaccessibility. Topics with lack of knowledge in order to utilise bioaccessibility data in risk assessment of human, oral exposure should be identified.

The contaminants selected for the review were selected heavy metals and polycyclic aromatic hydrocarbons (PAH):

As, Cd, Cr, Cu, Ni, Pb and Zn
fluoranthene, benzo(b+j+k)fluoranthenes, benzo(a)pyrene, dibenz(a,h)anthracene and indeno(1,2,3-cd)pyrene

These contaminants all have MCLs given as soil quality criteria and cleanup levels in Denmark /1/.

1.3 Methods

The information for the review was retrieved as a literature search in the databases STNEasy (chemical and environmental literature) and MEDLINE (medical literature), as well as with the web search engines Yahoo and Scirus. The web sites for the Environmental Protection Agency of the US (US EPA) and the US National Technical Information Service (NTIS) were searched as well.

Search terms were combinations of (? indicates truncation):

bioaccessibility, human uptake, human bioavailability, human absorption, oral bioavailability, systemic bioavailability (OR)
AND
PAH?, polycyclic aromatic hydrocarbon?, fluoranthene, benzo(b+j+k)fluoranthenes, benzo(a)pyrene, dibenz(a,h)anthracene indeno(1,2,3-cd)pyrene, metals, As, Cd, Cr, Cu, Ni, Pb, Zn (OR)
AND
soil

Search for test methods was further done with the terms:

oral, drug?, in vitro, bioaccessibility, test (AND)
oral, drug?, test?, dissolution (AND)

Cross references were retrieved subsequently and key author names were searched for additional references. Furthermore, the available information on the standardisation of bioaccessibility tests within the International Organization for Standardization (ISO) was included.

The references were filed in a Reference Manager system containing currently just over to 200 references.

Finally, the report was discussed at a workshop held in Copenhagen on March 17, 2003 and afterwards revised to reflect the conclusions at the workshop and additional material subsequently supplied by the workshop participants.

During the literature survey, a number of recent international reviews and textbooks on the topic, as well as a few basic textbooks were identified /2-17/. Text without references cited in this review are based upon these international reviews and textbooks.