Pollutants in Products Containing Activated Carbon: Improving Detection Methods and Legal Bases

Many consumer goods contain activated carbon, which can be contaminated with pollutants like polycyclic aromatic hydrocarbons (PAHs). Agroscope showed that current analytical methods and legal bases used to address PAH content are incomplete.

Toothpaste, soap, face masks, food colouring, charcoal flour, water filters, diarrhoea tablets: all these products contain or consist of activated carbon or biochar, used mainly to sequester pollutants, or to blacken food or personal care products.

Activated carbon often contains harmful PAHs

When these carbons are produced by pyrolysis – but also by barbecuing, smoking tobacco, smoking foods, volcanic eruptions, forest fires and the internal-combustion engine – PAHs, which in some cases remain attached to the carbon, are among the substances also produced. Not all of the many hundreds of individual substances are equally harmful, but Benzo[a]pyrene (BaP), perhaps the best-known example, is carcinogenic, genotoxic and reprotoxic.

When activated carbon products are used, PAHs can detach from the surface and enter the body via the skin, lungs and gastrointestinal tract, where they exert their effects. For this reason, consumer goods containing or consisting of activated carbon must meet certain quality standards, inter alia with regard to their PAH content. In this study, we show that the regulations governing PAH analysis and content are mostly inadequate and in some cases contradictory.

Optimisation potential of analytical methods and regulatory guidelines for PAHs in activated carbon

The inadequacies of the analytical methods currently used relate on the one hand to their extraction capabilities and on the other to their detection techniques. Thus, for example, solvents that are too weak are often used, with the result that the PAHs remain firmly attached to the activated carbon. In addition, the recommended extraction time is either too short, or not described at all. Depending on the legal guidelines, the techniques for detecting PAHs in the extract are either not specific enough, or not sensitive enough.

Elevated PAH content in some samples

In a further step, we purchased a range of products consisting of or containing activated carbon and analysed them for PAHs using a previously optimised analytical method for biochar (one of the many product categories of pyrogenic carbon-based materials). In eight out of 15 samples, concentrations of up to 30 mg/kg PAHs (sum of the 16 compounds prioritised by the US Environmental Protection Agency) and a BaP concentration of up to 1.4 mg/kg were detected. Such levels are well above the existing limit of the European Regulation on Food Additives, as well as the sectoral standard, the European Biochar Certificate. These findings show that products currently available on the market are not above reproach in terms of their PAH content – although the mechanisms of the formation and minimisation of PAHs during the production of carbon via pyrolysis are known, and thus furnish the basis for a more systematic regulation.