Chemicals in building materials have numerous valuable functions. However, hazardous chemicals in building materials risk contaminating waste streams and water streams, which may later influence humans, biodiversity, and ecosystem services if not appropriately managed (e.g., Bodar et al., 2018; Aurisano et al., 2021; Freige et al., 2018). In the case of implementing CE strategies, the chemicals in these secondary resources may hinder reuse and recycling, and there is a risk that dangerous chemicals cross-contaminate recycled and reused building products.
Reuse and recycling of construction materials can be hindered by the extensive contamination of preservatives, paints and glue, cross-contamination due to lack of selective demolition, legislation, and increased need for manual preparation for reuse (Vis et al., 2016). This highlights the need for material and context-specific risk assessment studies, as some recycled materials may contaminate the built environment. In some cases, hazardous substances from other industries are recycled into construction materials, e.g., ray tubes substituting sand in concrete production containing lead. Using ray tubes in concrete is considered safe because the lead will not release from the concrete. However, consequently, this will triple the amount of hazardous waste in the future, as concrete containing lead cannot currently be recycled (Bodar et al., 2018). Hazardous chemicals also challenge the reuse of building materials because few systems provide the necessary traceability for construction materials. According to Egebæk et al. (2019), the lack of traceability combined with the uncertainty of the chemical content is one of the leading barriers to the increased reuse of building components.
According to Bodar et al. (2018), the linear legislation on the use of chemicals problematises the transition to a circular economy. Currently, the REACH directive primarily hinders using hazardous chemicals in new products. However, it does not concern the waste management of products containing harmful chemicals, as this is a part of the Waste Framework Directive. A critical category (especially within the construction sector) is ‘legacy substances’, which are prohibited by law but are still a part of products currently in use. For instance, asbestos is not permitted in new building materials but is a part of many existing buildings (Bodar et al., 2018). These chemicals may reoccur in the end-of-life phase, when construction waste is deposited or recycled, representing a potential environmental risk for human health and the environment.
As the CE is gaining momentum, the need to reuse and recycle resources is demanded from governmental and non-governmental stakeholders. However, according to Bodar et al. (2019), these demands must balance resource efficiency targets, environmental safety, and public health targets. A more balanced approach could ensure the benefits of the CE and limit the negative consequences of, e.g., legacy substances.
When examining the linkage between CE and chemicals, green chemistry and the principles of green chemistry are reappearing concepts. According to Chen et al. (2020), integrating CE strategies within the principles of green chemistry would contribute to achieving the circular transition, as this would lessen the use and impact of hazardous chemicals. According to Silvestri et al. (2021), using Green Chemistry would contribute to more materials being reused and recycled.