Ecotoxicological impact of deactivated asbestos-cement on soil ecosystems

The effects of thermally deactivated asbestos cement (DAC) on the soil ecosystem were evaluated using the soil model organism Folsomia candida (Collembola). Two materials were obtained by treating asbestos cement slates, commonly used for roofing, at 1100 °C under oxidizing conditions (Red DAC) and at 1150 °C under reducing conditions (Green DAC). Ten age-synchronized juveniles of F. candida were exposed to DAC powder:soil mixtures in ratios of 1:1 and 1:10 for both types. After 28 days, adults and juveniles were counted to assess treatment effects. The results indicate distinct toxicity profiles. The Red powder did not induce adult lethality at the tested concentrations; however, a significant reduction in juvenile production was observed at the higher concentration (1:1). In contrast, the Green powder caused adult lethality at 1:1 concentration, with no juveniles produced. Both materials contain a high percentage of silica glass (∼40% by weight), a well-known insect dehydration agent and mechanical insecticide. At the highest concentration, silica glass may cause detrimental effects on juveniles, which are more sensitive to dehydration than adults. Green DAC also contains 8.5% lime (CaO), an antimicrobial and insecticidal agent that can disrupt soil pH. The combination of silica-induced dehydration and lime-mediated alkalinity may account for the lethal effects of Green DAC on F. candida adults. These findings reinforce the need for proper DAC recycling. While asbestos deactivation effectively eliminates its hazard in the built environment, improper disposal or soil contamination may pose ecological risks. Recycling DAC into stable matrices, such as ceramics or mortar, minimizes environmental contamination while promoting circular economy.