Characterization and management of asbestos containing soil during remediation

Asbestos is a common, commercial term which refers to the following fibrous silicates: chrysotile, crocidolite, amosite, actinolite, anthophyllite and tremolite. The first three of them have been mined and used worldwide in the last decades, because of their suitable technological features. The others occur in natural outcrops or as contaminants in some manmade products. When released or concentrated by natural or anthropic factors, asbestos is a persistent contaminant of soils, especially within urban and industrial areas, together with other pollutants such as polyaromatic hydrocarbons, lead or copper. Its health risk is mainly due to airborne asbestos, including the fibers released from soils, causing long-term health consequences if inhaled, with increased mortality from lung cancer and mesothelioma. Existing policies in various sectors such as agriculture, water, waste, chemistry and the prevention of industrial pollution contribute to the protection of the soil, which still shows some shortcomings, with respect to asbestos, for which the main regulations concern atmospheric emissions, discharges into the aquatic environment and the management of asbestos-containing waste (ACW). Rules and standards concerning asbestos risk prevention, reduction and control were developed to reduce the well-known health effects caused by inhalation. In Countries that banned the extraction, production and use of these minerals, important sources of airborne Asbestos are the Contaminated Soils (ACS) in brownfield sites. Typical examples of brownfield sites are former asbestos mines, industrial plants (eventually producing ACMs), demolition sites and illegal dumping. Their classification is mainly based on the risk grade, related to the extent, the number and the kind of sources. Therefore, the number of small sites could result even two to three orders of magnitude greater than the big ones. In Italy, for example, there are 11 Superfund sites which are mainly contaminated by asbestos, including the largest European former mine. On the other hand, the same Country hosts more than 100.000 sites with presence of medium and small asbestos sources – mainly ACMs. To a less extent, soils and sediments, including natural occurring asbestos, may constitute a health risk, too. Finally, natural disasters such as earthquakes, windstorm, fire or floods may greatly increase the risk of exposure to asbestos, eventually released in the environmental matrixes, including soil, from the embedding materials. Remediation and demolition activities carried out within the mentioned sites require to assess the health risks and thus a proper characterization of soil and sediments be conducted. For this purpose, suitable parts of different rules and standards are usually adopted, which involve laboratory analyses. Sampling of potentially contaminated soils should be compliant with the standard methods regarding soil assessment and sampling design, such as the ISO 10381 and the EPA/600/R-92/128. Furthermore, specific indications may come from local Environmental and Control Bodies, especially for the management of large brownfields and Superfund sites. To detect the soil contamination, some Countries adopted concentration thresholds or investigation criteria and use them also as remediation goals (e.g. Italy, Western Australia), while others use only values deriving from site-specific risk assessment (e.g. USA). As regards the analytical methods, usually the laboratories apply the regulations designed to detect and quantify the asbestos content in manmade bulk materials (ACMs), such as the asbestos cement products. The main analytical techniques are the optical and electronic microscopy, the X-Ray diffraction and the infrared spectroscopy. Unfortunately, there are no consolidated methods able to reach the sensitivity required for soil analysis (the threshold value order of magnitude is 0,01% by weight) without the need of complex sample treatments, which in turn contribute to the increase of the uncertainty. Further research is thus needed. Depending on the applied regulations and the results of risk assessment – i.e. in most cases when the analytical concentration exceeds the threshold - the ACS become a waste. This condition requires proper management of the ACW (including treatments, transport, further laboratory analyses and disposal) with the aim of protecting the human health. This work will briefly describe the methods and the techniques usually carried on soils with a potential or confirmed contamination by asbestos fibers, with the scope to characterize, classify and manage properly the related ACW. Some interesting, unconventional techniques will also be described, with the advantages of both portability and no sample treating need, which therefore should be tested on soil samples.