Increased Temperature and Turbulence Alter the Effects of Leachates from Tire Particles on Fathead Minnow (Pimephales promelas).

Tire particles are of concern as a stressor due to the combination of their chemical constituents, high emission rates, and global distribution. Once in the environment, they will interact with physical parameters (e.g., UV, temperature). The interaction of chemical pollution with changing physical environmental parameters is often underestimated in ecotoxicology. Here, we investigate the role of temperature, mechanical stress (i.e., turbulence), UV, and CO2 on the effects of tire leachates on fish. Two samples of tire particles were exposed to four different levels of each physical stressor. A toxicological assessment was performed with fathead minnow embryos assessing five end points (hatching success, time to hatch, length, deformities, and heart rate). Results showed that variations of temperature and mechanical stress affect the toxicological impact of tire leachates. Zn and/or polycyclic aromatic hydrocarbons (pyrene, phenanthrene, chrysene, benzo[a]pyrene, anthracene, naphthalene, fluoranthene, and benzo[ghi]perylene) were identified in the leachate and tire samples by Raman/surface-enhanced Raman spectroscopy and gas chromatography with mass spectroscopy, respectively.

Chronic Embryo-Larval Exposure of Fathead Minnows to the Pharmaceutical Drug Metformin: Survival, Growth, and Microbiome Responses.

Metformin is a glucose-lowering drug commonly found in municipal wastewater effluents (MWWEs). The present study investigated the chronic effects of metformin in early-life stages of the fathead minnow (Pimephales promelas). Endpoints assessed were growth, survival, and deformities. The larval gut microbiome was also examined using 16 S ribosomal RNA gene amplicon sequencing to determine microbial community composition and alpha and beta diversity. Eggs and larvae were exposed to metformin measured concentrations (mean [standard deviation]) of 0.020 (0.017) µg/L (for controls) and 3.44 (0.23), 33.6 (1.6), and 269 (11) µg/L in a daily static-renewal setup, with 20 embryos per beaker. The low and middle metformin exposure concentrations represent river and MWWE concentrations of metformin. To detect small changes in growth, we used 18 replicate beakers for controls and 9 replicates for each metformin treatment. Over the 21-d exposure (5 d as embryos and 16 d posthatch [dph]), metformin did not affect survival or growth of larval fish. Hatch success, time to hatch, deformities in hatched fry, and survival were similar across all treatments. Growth (wet wt, length, and condition factor) assessed at 9 and 16 dph was also unaffected by metformin. Assessment of the microbiome showed that the larvae microbiome was dominant in Proteobacteria and Firmicutes, with small increases in Proteobacteria and decreases in Firmicutes with increasing exposure to metformin. No treatment effects were found for microbiome diversity measures. Control fish euthanized with the anesthetic tricaine methane sulfonate had decreased alpha diversity compared to those sampled by spinal severance. This experiment demonstrates that metformin at environmentally relevant concentrations (3.44 and 33.6 µg/L) and at 10 times MWWE concentrations (269 µg/L) does not adversely affect larval growth or gut microbiome in this ubiquitous freshwater fish species. Environ Toxicol Chem 2022;41:635-647. © 2021 Her Majesty the Queen in Right of Canada. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. Reproduced with the permission of the Minister of Environment and Climate Change Canada.

A Deep Dive into the Complex Chemical Mixture and Toxicity of Tire Wear Particle Leachate in Fathead Minnow.

The ecological impact of tire wear particles in aquatic ecosystems is a growing environmental concern. We combined toxicity testing, using fathead minnow (Pimephales promelas) embryos, with nontarget high-resolution liquid chromatography Orbitrap mass spectrometry to characterize the toxicity and chemical mixture of organic chemicals associated with tire particle leachates. We assessed: 1) exposure to tire particle leachates after leaching for 1-, 3-, and 10-d; and 2) the effect of the presence and absence of small tire particulates in the leachates. We observed a decrease in embryonic heart rates, hatching success, and lengths, as well as an increase in the number of embryos with severe deformities and diminished eye and body pigmentation, after exposure to the leachates. Overall, there was a pattern whereby we observed more toxicity in the 10-d leachates, and greater toxicity in unfiltered leachates. Redundancy analysis showed that several benzothiazoles and aryl-amines were correlated with the toxic effects observed in the embryos. These included benzothiazole, 2-aminobenzothiazole, 2-mercaptobenzothiazole, N,N'-diphenylguanidine, and N,N'-diphenylurea. However, many other chemicals characterized as unknowns are likely to also play a key role in the adverse effects observed. Our study provides insight into the types of chemicals likely to be important toxicological drivers in tire leachates, and improves our understanding of the ecotoxicological impacts of tire wear particles. Environ Toxicol Chem 2022;41:1144-1153. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Potential endocrine disruption of sexual development in free ranging male northern leopard frogs (Rana pipiens) and green frogs (Rana clamitans) from areas of intensive row crop agriculture.

Intensive row crop agriculture (IRCA) for corn and soybean production is predominant in eastern and central North America. IRCA relies heavily on pesticide and nutrient inputs to maximize production under conventional systems. In 2003-2005, we assessed the occurrence of a suite of potential endocrine effects in amphibians inhabiting farm ponds and agricultural drains in IRCA areas of southwestern Ontario. Effects were compared to amphibians from two agricultural reference sites as well as four non-agricultural reference sites. Pesticide and nutrient concentrations were also determined in water samples from those sites. Atrazine and metolachlor were detected in most samples, exceeding 1 microg L(-1) at some sites. Blood samples were taken from northern leopard frogs (Rana pipiens) and green frogs (Rana clamitans) for analysis of circulating sex steroids and vitellogenin-like protein (Vtg-lp), a biomarker of exposure to environmental estrogens. Gonads were histologically examined for evidence of abnormalities. Some evidence of exposure to endocrine disrupting compounds was apparent from the data. The occurrence of testicular ovarian follicles (TOFS) in male R. pipiens was significantly higher (42%; p<0.05) at agricultural sites, particularly those in Chatham county compared to frogs from reference sites (7%). There was no difference in circulating sex steroid levels between frogs from agricultural and reference sites and sex steroid levels did not correlate with pesticide concentrations in the environment. No differences were detected in the gonadosomatic indices or stage of spermatogenesis between frogs from agricultural and non-agricultural regions (p>0.05). Plasma Vtg-lp was detected in only one male R. pipiens from an agricultural site. Neither gonad size, gonad maturity nor sex steroid levels differed between normal males and those with testicular oocytes. Although the proportion of testicular oocytes did not correlate directly with atrazine concentrations, it did correlate with a mixture of pesticides and nutrients, particularly atrazine and nitrate, while the number of pesticides detected at each site was also important.