Aquatic toxicity of waterpipe wastewater chemicals

The recent increase in U.S. popularity and use prevalence of water pipe (WP) tobacco smoking raises concerns about the potential environmental impacts of WP waste disposal and the need for strategies to reduce such impacts. The U.S. Food and Drug Administration (FDA) is required to assess the environmental impacts of its tobacco regulatory actions per the U.S. National Environmental Policy Act (NEPA). The purpose of this study was to identify and quantify specific chemical constituents in WP wastewater and to determine their potential aquatic toxicity.

Using a modified Beirut smoking regimen, five different WP charcoal brands (n = 70) and ten WP tobacco brands (n = 35) were smoked separately using a WP smoking machine in which smoke was passed through the WP base water. We analyzed and quantified specific chemical constituents in the WP bowl wastewater through standardized U.S. Environmental Protection Agency's (EPA) Hazardous Waste Test Methods. We then characterized the ecological hazard for acute and chronic aquatic toxicity posed by the specific chemicals through compilations of Globally Harmonized System of Classification and Labelling of Chemicals (GHS) and hazardous concentration values (concentration affecting 50% of the species).

Among the list of 31 specific chemicals analyzed, we detected 22 and 11 chemicals in wastewater from WP tobacco and WP charcoal smoking, respectively. Nearly half of the 22 WP wastewater chemicals were classified as "very toxic" or "toxic" for acute and chronic aquatic toxicity per GHS classification. The most hazardous compounds with acute and chronic toxicity in aquatic organisms include acrolein, acrylonitrile, and metals (cadmium, lead, chromium, nickel, cobalt) found in both WP tobacco and charcoal wastewater, and N-nitrosonornicotine, nicotine, crotonaldehyde and selenium were additionally found in WP tobacco wastewater. All the identified chemicals are considered harmful or potentially harmful constituents in tobacco products and tobacco smoke per FDA's list, and seventeen of them represent hazardous waste per EPA's list.

Our study expands the identification and quantifies several WP wastewater chemical constituents. It characterizes the ecological hazard of these chemicals and identifies chemicals of concern, aiding our evaluation of the environmental impacts of WP waste products. Our results add to the existing evidence that WP wastewater is a source of toxins that could affect water quality and aquatic organisms, and bioaccumulate in the environment if disposed of into public sewers, on the ground, or in an onsite septic system. These findings highlight the importance of concerted efforts to raise awareness of appropriate WP waste disposal practices in both retail and residential settings, and applicable regulatory compliance requirements for WP retailer establishments, thereby limiting hazards from WP wastewater.