W illiams Kwari Joshua and Yaduma Gaiuson W andiahyel /Afr.J.Bio.Sc. 3(2) (2021) 42-49 Page 42 of 49 Volume 3, Issue 2, April 2021 Received : 13 August 2020 Accepted : 16 November 2020 Published : 05 April 2021 doi: 10.33472/AFJBS.3.2.2021.42-49 Article Info © 2021 African Journal of Biological Sciences. This is an open access article under the CC BY license (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. A bstract Pharmaceuticals and personal care products are now known as micro- contaminants due to their effects on bacterial resistance and effect on non-targeted organisms. Most recently, these substances have been found in surface water, sewage, hospital and care home wastewaters and landfill. Pharmaceuticals have been known to pose acute and chronic effects especially when exposed at higher concentrations and for longer durations. This study adopted the spectrophotometric method to assess the acute and chronic effects of seven pharmaceuticals on Bacillus subtilis bacteria. The effects were observed in terms of the conversion of 3-(4.5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)- 2-(4-sulfophenyl)-2H-tetrazolium, inner salt; (MTS) to a colored formazan product. The effect of pharmaceuticals was measured as a reduction of tetrazolium solution and expressed as percentage. The results indicate that both acute and chronic effects exist with Bezafibrate, Diclofenac, Diatrizoate, Ibuprofen and Atenolol inhibiting bacterial growth at 50 μg/ml. Consequently, at 500 μg/ml, all the pharmaceuticals inhibited growth thereby posing acute effects. In addition, all the eight pharmaceutical substances tested inhibited bacterial growth at 50 μg/ml and 500 μg/ml when exposed to pharmaceuticals for more than 24 h. The implication is that wastewater from hospitals can likely inhibit biological process of breaking waste in the wastewater treatment plants. Keywords: Pharmaceuticals, Toxicity, W astewater, Bacteria, Bacillus subtilis 1. Introduction In the past, the composition of substances that contaminate the environment were centered around heavy metals and emissions from factories as a result of industrialization (Cioca and Munteanu, 2019; Veras et al., 2019; White et al., 2019). However, in recent times, the attention of contaminants is gradually changing from the previously known contaminants to micro contaminants (Cabral et al., 2019; Fick et al., 2009). These micro contaminants include organic chemicals, pesticides, pharmaceuticals and plastics have been found in the environment in several samples at different places and concentrations (Kümmerer et al., 2019; Pal et al., 2010). These toxic substances have been known to enter the environment via hospitals, care homes, production industries, household waste and wastewater (Bonnefille et al., 2018; Hu et al., 2018; Verlicchi et al., 2010). Although their toxic effects have widely been studied in recent years, they continue to persist in the environment at concentrations that can likely cause severe impacts. * Corresponding author: Williams Kwari Joshua, Faculty of Pure and Applied Sciences, Federal University Wukari, Taraba State, Nigeria. E-mail: kwariwills@gmail.com 2663-2187/© 2021 African Journal of Biological Sciences. All rights reserved. African Journal of Biological Sciences ISSN: 2663-2187 Journal homepage: http://www.afjbs.com The use of Bacillus subtilis bacteria as a tool to assess the toxicity of pharmaceuticals in the environment Williams Kwari Joshua 1* and Yaduma Gaiuson Wandiahyel 2 1 Faculty of Pure and Applied Sciences, Federal University Wukari, Taraba State, Nigeria. E-mail: kwariwills@gmail.com 2 Department of Chemistry, Adamawa State College of Education, Hong, Adamawa State, Nigeria. E-mail: wandiayaduma@gmail.com Research Paper Open Access W illiams Kwari Joshua and Yaduma Gaiuson W andiahyel /Afr.J.Bio.Sc. 3(2) (2021) 42-49 https://doi.org/10.33472/AFJBS.3.2.2021.42-49