Description

Cigarette butts are one of the most common forms of litter in the environment today. Each cigarette contains numerous toxic chemical contaminants such as arsenic, nicotine, polycyclic aromatic hydrocarbons (PAHs), formaldehyde, and lead. While a majority of these compounds are well-known carcinogens, reproductive toxicants, or toxic to other systems, hundreds of additional chemical constituents and their transformed products have yet to be toxicologically profiled. The goal of our study was to assess whether cigarette butt litter impacts embryonic development, using the zebrafish as an aquatic model that also translates to human development. Zebrafish embryos were exposed to cigarette butt leachates at concentrations of 0, 0.1, 0.5, or 1 cigarette butt per liter from 1-4 days post fertilization (dpf). Morphological development, survival, and metabolic activity were observed using quantitative microscopy. Decreased fish length, impaired liver development, and increased yolk edema were observed in exposed embryos. Embryos were also co-exposed to 7-ethoxyresorufin, a non-toxic chemical that becomes fluorescent when metabolized by Cyp1a--a xenobiotic metabolizing enzyme. Fluorescence was significantly decreased due to cigarette butt leachate exposure. From these results, we conclude that embryonic development is impaired due to cigarette butt leachate exposures, namely hindering growth, inducing edema, and decreased Cyp1a activity. This research demonstrates a clear anthropogenic risk to aquatic ecosystems, as well as human health, since many of these compounds bioaccumulate before fish and other species are consumed by humans. Though cigarette butts may be characterized as hazardous wastes in California, more emphasis on convenient and abundant disposal opportunities would help to reduce these products from deposition into our waterways, preventing this environmental challenge.