Vol.:(0123456789) 1 3 Environmental Chemistry Letters https://doi.org/10.1007/s10311-019-00918-5 ORIGINAL PAPER Dish handwashing: an overlooked source of contamination Mojca Bavcon Kralj 1  · Anja Fortuna 1  · Anže Abram 2  · Polonca Trebše 1 Received: 25 April 2019 / Accepted: 23 July 2019 © Springer Nature Switzerland AG 2019 Abstract Daily dishwashing is a common household activity. Washing dishes in a sink is considered safe for the environment because it requires few water and human energy. There are concerns, however, that residues from the detergent used may impact health and the environment. Here, we studied the adsorption and toxicity of two detergent ingredients, the biocide 1,2-benzi- sothiazol-3(2H)-one and the surfactant sodium dodecyl sulphate, left on tableware, cups and plates, made of glass, stainless steel, ceramic, plastic and wood. Results show that levels of biocide and surfactant residues were much higher on wooden plates, of 8.4 ng biocide cm −2 and 226.4 ng surfactant cm −2 , than on glass, of 0.9 ng biocide cm −2 and 55.9 ng surfactant cm −2 . Residues levels increase with material roughness. Toxicity analysis of compounds in water using the luminiscence of Vibrio fischeri revealed that toxic inhibition was much higher (20%) when the biocide and the surfactant were together than when the surfactant occurred alone (1.9%) or the biocide occurred alone (11.5%). Overall, our fndings imply that, depending on the dish material and roughness, contaminants will be transferred either to humans through eating using contaminated dishes, or to wastewater and then to humans indirectly through contamination of natural waters. Keywords 1,2-benzisothiazol-3(2H)-one · Sodium dodecyl sulphate · Toxicity test · Detergent · Roughness of surfaces Introduction Washing dishes is a routine household activity, which depends on human habits and practices. Its efficiency depends on consumer behaviour, techniques for the washing- up and the quantity of resources such as water, energy, time and cleaning products (Garcia-Hidalgo et al. 2017). There are several diferent ways this is done: washing under a run- ning tap and washing in one or two sinks. In the discourse on climate change and the scarcity of resources, the house- hold is the centre of changing human behaviour. Washing under running tap water is the predominant method (45%), whereas the consumers from regions less rich in water, from Australia, New Zealand and Southern Africa, and 51% of the German population prefer a sink flled with water, named Tip 1 in Best Practice Tips in the applicable guide for consumers (Fuss et al. 2011; Berkholtz et al. 2013; Gilleßen et al. 2013). Surfactants are one of the main components of detergents, and these have changed little over the years (Gambogi et al. 2009). Sodium dodecyl sulphate is one of the most com- monly used surfactants in dishwashing liquid as a foam- ing agent. Its use is advised against in dishwashers, where instead foam inhibitors are applied. There are many litera- ture data about health consequences and benefts of its use (Bondi et al. 2015; Rebello et al. 2014; Scanlan et al. 2017). Unfortunately, much of the literature reviewing the impacts of sodium dodecyl sulphate residues is outdated (Rieger 1994; Schlüßler 1980); however, according to guidelines published by the Food and Drink Administration (FDA) (21 CFR 172.822, 2015), its use as a food additive is permitted in food for direct human consumption. Recently, a serious source of the pollution of municipal wastewaters coming from dishwashing is the added biocides in detergents. One such 1,2-benzisothiazol-3(2H)-one, for example, is used as a preservative in detergents, and it has lately been found in all examined wastewaters in a survey from North Germany (Wieck et al. 2018). Usually, bioc- idal active substances do not have only one function, and in fact, 1,2-benzisothiazol-3(2H)-one plays a signifcant role * Polonca Trebše polonca.trebse@zf.uni-lj.si 1 Faculty of Health Sciences, University of Ljubljana, 1000 Ljubljana, Slovenia 2 Department for Nanostructured Materials, Jožef Stefan Institute, 1000 Ljubljana, Slovenia