The Society of Environmental Toxicology and Chemistry (SETAC) held its 43^rd Annual Meeting in November in Pittsburgh, PA. Smithers experts presented various topics, along with other conference participants, around the theme of “Bridging Innovation and Sustainability”  in environmental toxicology.

Dr. Kalumbu Malekani, Chief Scientific Officer, Smithers Environmental Risk Sciences Division, attended the conference and shared the following highlights in the areas of Ecotoxicology and Environmental Fate:

Experts discussed alternatives to animal testing such as using new approach methodologies (NAMs) like an automated in vitro method for fish testing as an alternative to the OECD test guideline (TG) 203 (T. D. Lunsman, Corteva Agriscience). Researchers used rainbow trout gill cell line (RT gill-W1) to provide an in vitro alternative to in vivo testing to predict the acute fish toxicity test. Unlike in the OECD 249, where a reduction in fluorescence is used to assess cell viability, this NAM technique leveraged the RT gill-W1 cell line to measure luminescent ATP in an in vitro cytotoxicity test. This in vitro NAM generated results comparable to OECD TG 249 in a faster and more efficient way.

A presentation on “Abiotic RNA Hydrolysis in the environment: Implications for the Environmental Fate of Emerging RNA Interference Biopesticides,” showcased results from the abiotic hydrolysis of dsRNA in surface waters, soils, and sediments. RNA interference (RNAi) is a biological process in which a double-stranded (ds)RNA directs the degradation of homologous messenger RNA (mRNA), preventing protein synthesis. Several RNAi-based products developed using dsRNA have applications in agriculture as dsRNA biopesticides to protect crops from pests.

This research contributed to the fundamental understanding of the chemical stability of dsRNA molecules and their ultimate potential to persist in biological and environmental systems in the absence of enzymes or microorganisms. The results demonstrated that in environmental compartments (soil, sediment, or surface waters) nucleic acids, including dsRNA, are distributed between dissolved molecules and molecules adsorbed to various minerals, including metal (oxyhydr)oxides. Dissolved single-stranded (ss)RNA underwent rapid hydrolysis catalyzed by alkaline pH and at neutral pH by certain metal ions (i.e., lead and copper) that accelerate hydrolysis by acting as Lewis acids. It was observed that dissolved dsRNA was stable to abiotic hydrolysis likely due to the rigidity of its duplex structure. It is postulated that mineral-catalyzed hydrolysis may be a significant pathway for the degradation of RNAi-based biopesticides in environmental systems. There is still a need to evaluate the environmental fate of RNAi-based biopesticides in a formulation.

In “Leveraging Sustainability Initiatives to Provide FIFRA/ESA Mitigation,” EPA announced an ESA Workplan Update providing details on how EPA plans to pursue protections for nontarget species earlier in the process for pesticide registration review and other FIFRA actions to meet the ESA requirements fully.

Workplan Update highlights:

• Section II provides an overall approach to mitigating ecological risks during the registration review. For any pesticide that poses ecological risks, the Agency expects to include interim mitigation measures to reduce exposure to nontarget species, including listed species.
• Section III, EPA provides a list of mitigation measures that can be used across various pesticides to reduce exposure to nontarget species, including measures to reduce spray drift, runoff, and pesticide transport through erosion.
• Section V provides updates on other strategies to expedite the implementation of the ESA Workplan, especially strategies to prioritize mitigation for listed species vulnerable to pesticides and to improve the efficiency and timeliness of the pesticide consultation process.

Other hot topics included microplastics in the environment and risk assessment, the microbiome as an emerging tool for predictive ecotoxicology, and PFAS-related fish advisories.

Contact us to hear more about these topics or to meet with our team at SETAC Europe in Dublin, April 30 – May 4, 2023.