ABSTRACT
Antimicrobial resistance (AMR) is one of the world's industrialized nations' biggest issues. It has a significant influence on the ecosystem and negatively affects human health. The overuse of antibiotics in the healthcare and agri-food industries has historically been defined as a leading factor, although the use of antimicrobial-containing personal care products plays a significant role in the spread of AMR. Lotions, creams, shampoos, soaps, shower gels, toothpaste, fragrances, and other items are used for everyday grooming and hygiene. However, in addition to the primary ingredients, additives are included to help preserve the product by lowering its microbial load and provide disinfection properties. These same substances are released into the environment, escaping traditional wastewater treatment methods and remaining in ecosystems where they contact microbial communities and promote the spread of resistance. The study of antimicrobial compounds, which are often solely researched from a toxicological point of view, must be resumed considering the recent discoveries, to highlight their contribution to AMR. Parabens, triclocarban, and triclosan are among the most worrying chemicals. To investigate this issue, more effective models must be chosen. Among them, zebrafish is a crucial study system because it allows for the assessment of both the risks associated with exposure to these substances as well as environmental monitoring. Furthermore, artificial intelligence-based computer systems are useful in simplifying the handling of antibiotic resistance data and speeding up drug discovery processes.
ABSTRACT
Living and working environments are most often closed spaces where it is necessary to provide health protection for family members and employees. Some activities require special protection, especially during a pandemic. The living and working environments can be kept clean and tidy in three ways: by cleaning, disinfecting, and sanitising. This paper presents a review of the literature linking disinfectants, their use, and resistance of microorganisms to disinfectants. In addition, it gives an overview of critical points that have arisen in various testing laboratories in the Republic of Croatia, related to the COVID-19 pandemic, and as a consequence of the lack of guidelines in norms. The literature search was conducted based on the keyword 'disinfection' in PubMed, Science Direct, Web of Science, Scopus and Google Scholar databases, and on the CDC and HZJZ websites due to the latest recommendations regarding COVID-19 infections. Results have shown that a norm is a basic document that needs a specific upgrade depending on the type of laboratory and its activities, and it should not be an independent decision of each individual laboratory. Based on the identified needs and problems, state institutions should provide detailed instructions depending on the laboratory activity. Therefore, this situation and the experience gained should be used as a starting point for document development that could be applicable in crisis states generally. In addition, it could be used as a basis for education and training in crisis states.
ABSTRACT
Triclosan (TCS) has been proved to have a harmful effect on human health and ecological environment, especially during the COVID-19 epidemic, when plentiful antibacterial hand sanitizers were discharged. Manganese dioxide (MnO2) showed a good effect on the removal of TCS. The morphology of MnO2 was regulated in this study to increase the active sites for removing TCS and improve the removal effect. The results showed that nanoflower T-MnO2 exhibited best removal efficiency due to its high oxygen vacancy, high Mn3+ content, easily released lattice oxygen and unique tunnel structure which make its Mn-O bond easier to activate. Further study of the mechanism revealed that the process of removing TCS by MnO2 was the first adsorption and then oxidation process and the detailed reaction process was clarified. 3-chlorophenol and 2,4-dichlorophenol were proved to be their oxidative product. Additionally, it was verified that oxidation dominated in the removal of TCS by MnO2 rather than adsorption through Density functional theory (DFT) calculations analysis. It is determined that nanoflower MnO2 was a promising material for removing TCS.
ABSTRACT
The COVID-19 pandemic increased the pollution of water resources by some contaminants, e.g., chloroquine (CQN), due to its probable benefit in the treatment of the virus. Thus, is necessary the removal of CQN from water through advanced techniques. Black soybeans have been widely used due to their benefits to human health, and as a result, there was an increase in soybean husk residue, the main by-product of the soybean processing industry. Given the current scenario and the need to develop new uses for this agricultural residue, this study aimed to establish an economical and environmental biotechnology by the CQN adsorption process onto black soybean hulls (BSH) for the first time. BSH was characterized by physicochemical and spectroscopic techniques that demonstrated porosity, organic functional groups and negative surface charges. The pH study did not affect CQN adsorption pronouncedly, indicating that π-interactions and hydrogen bonds are the main mechanisms of the adsorption process. The maximum adsorption capacity was 75.06 ± 2.24 mg g−1 with 240 min of contact time at 288 K. In order to verify the biosorbent applicability, the safranin orange dye and triclosan adsorption were also evaluated onto BSH. The absorption peaks of the contaminants used in the synthetic mixture demonstrated a removal rate of 90.81 ± 0.80% for safranin orange, 66.79 ± 1.12% for triclosan and 70.62 ± 0.67% for CQN. The satisfactory removal of other contaminants indicates that BSH is a promising, affordable and environmentally friendly biosorbent with applicability potential for alternative treatment of contaminated water. © 2023 Taylor & Francis Group, LLC.
ABSTRACT
With the COVID-19 pandemic, the use of disinfectants has grown significantly around the world. Triclosan (TCS), namely 5-chloro-2-(2,4-dichlorophenoxy) phenol or 2,4,4'-trichloro-2'-hydroxydiphenyl ether, is a broad-spectrum, lipophilic, antibacterial agent that is extensively used in multifarious consumer products. Due to the widespread use and bioaccumulation, TCS is frequently detected in the environment and human biological samples. Accumulating evidence suggests that TCS is considered as a novel endocrine disruptor and may have potential unfavorable effects on human health, but studies on the toxic effect mediated by TCS exposure as well as its underlying mechanisms of action are relatively sparse. Therefore, in this review, we attempted to summarize the potential detrimental effects of TCS exposure on human reproductive health, liver function, intestinal homeostasis, kidney function, thyroid endocrine, and other tissue health, and further explore its mechanisms of action, thereby contributing to the better understanding of TCS characteristics and safety. Moreover, our work suggested the need to further investigate the biological effects of TCS exposure at the metabolic level in vivo.
Subject(s)
COVID-19 , Triclosan , Humans , Triclosan/toxicity , Triclosan/metabolism , Pandemics , Phenol , Anti-Bacterial AgentsABSTRACT
The present study deals with the synthesis and characterization of a polymer composite based on an unsaturated ester loaded with 5 wt.% triclosan, produced by co-mixing on an automated hardware system. The polymer composite's non-porous structure and chemical composition make it an ideal material for surface disinfection and antimicrobial protection. According to the findings, the polymer composite effectively inhibited (100%) the growth of Staphylococcus aureus 6538-P under exposure to physicochemical factors, including pH, UV, and sunlight, over a 2-month period. In addition, the polymer composite demonstrated potent antiviral activity against human influenza virus strain A and the avian coronavirus infectious bronchitis virus (IBV), with infectious activities of 99.99% and 90%, respectively. Thus, the resulting triclosan-loaded polymer composite is revealed to have a high potential as a surface-coating non-porous material with antimicrobial properties.
ABSTRACT
Environmental-friendly and efficient strategies for triclosan (TCS) removal have received more attention. Influenced by COVID-19, a large amount of TCS contaminants were accumulated in medical and domestic wastewater discharges. In this study, a unique g-C3N4/Bi2MoO6 heterostructure was fabricated and optimized by a novel and simple method for superb photocatalytic dechlorination of TCS into 2-phenoxyphenol (2-PP) under visible light irradiation. The as-prepared samples were characterized and analyzed by XRD, BET, SEM, XPS, etc. The rationally designed g-C3N4/Bi2MoO6 (4:6) catalyst exhibited notably photocatalytic activity in that more than 95.5% of TCS was transformed at 180 min, which was 3.6 times higher than that of pure g-C3N4 powder. This catalyst promotes efficient photocatalytic electron-hole separation for efficient dechlorination by photocatalytic reduction. The samples exhibited high recyclable ability and the dechlorination pathway was clear. The results of Density Functional Theory calculations displayed the TCS dechlorination selectivity has different mechanisms and hydrogen substitution may be more favorable than hydrogen ion in the TCS dechlorination hydrogen transfer process. This work will provide an experimental and theoretical basis for designing high-performance photocatalysts to construct the systems of efficient and safe visible photocatalytic reduction of aromatic chlorinated pollutants, such as TCS in dechlorinated waters. © 2022 Elsevier Ltd
ABSTRACT
Triclosan (TCS) has been widely used in daily life because of its broad-spectrum antibacterial activities. The residue of TCS and related compounds in the environment is one of the critical environmental safety problems, and the pandemic of COVID-19 aggravates the accumulation of TCS and related compounds in the environment. Therefore, detecting TCS and related compound residues in the environment is of great significance to human health and environmental safety. The distribution of TCS and related compounds are slightly different worldwide, and the removal methods also have advantages and disadvantages. This paper summarized the research progress on the source, distribution, degradation, analytical extraction, detection, and removal techniques of TCS and related compounds in different environmental samples. The commonly used analytical extraction methods for TCS and related compounds include solid-phase extraction, liquid-liquid extraction, solid-phase microextraction, liquid-phase microextraction, and so on. The determination methods include liquid chromatography coupled with different detectors, gas chromatography and related methods, sensors, electrochemical method, capillary electrophoresis. The removal techniques in various environmental samples mainly include biodegradation, advanced oxidation, and adsorption methods. Besides, both the pros and cons of different techniques have been compared and summarized, and the development and prospect of each technique have been given.
Subject(s)
COVID-19 , Triclosan , Humans , Triclosan/analysis , Chromatography, Liquid , Anti-Bacterial Agents , Solid Phase ExtractionABSTRACT
The concentration of triclosan in wastewater is expected to rise dramatically as a consequence of the COVID-19 pandemic. A modeling analysis of the growth kinetics of microbial culture during triclosan degradation was necessary in order to establish effective wastewater treatment. The kinetic parameters are used by engineers to aid in the design and process control of biological processes. Studies were conducted using triclosan-acclimated culture to examine biomass growth and associated substrate degradation at different initial substrate concentrations (0.35–4.9 mg L−1) to this end. Substrate inhibition was calculated from experimental growth parameters using unstructured kinetic models. Unlike other model studies, a time-averaged specific bacterial growth rate in the log phase was considered for kinetic models in this study. Overestimation of the conventional log phase calculation for unstructured kinetic model constants was eliminated when the slowdown growth part of the log growth phase was taken into account. The Haldane Model was more accurate to fitting experimental data in an excellent manner. In this case, the time-averaged specific growth rate, saturation constant, and inhibition constant were 0.56 h−1, 12.77 mg L−1, 0.52 mg L−1, respectively. A yield coefficient of 0.404 mgX.mgS−1 was calculated. The critical triclosan concentration was 2.57 mg L−1. Wastewater treatment plants can be more sensitive to the value of the critical triclosan concentration. The value for time-averaged critical specific growth rate was 0.051 h−1. Pre-or post-treatment requirements can be estimated using time-averaged critical growth rate values as a benchmarking tool in biological treatment systems.
ABSTRACT
Environmental-friendly and efficient strategies for triclosan (TCS) removal have received more attention. Influenced by COVID-19, a large amount of TCS contaminants were accumulated in medical and domestic wastewater discharges. In this study, a unique g-C3N4/Bi2MoO6 heterostructure was fabricated and optimized by a novel and simple method for superb photocatalytic dechlorination of TCS into 2-phenoxyphenol (2-PP) under visible light irradiation. The as-prepared samples were characterized and analyzed by XRD, BET, SEM, XPS, etc. The rationally designed g-C3N4/Bi2MoO6 (4:6) catalyst exhibited notably photocatalytic activity in that more than 95.5% of TCS was transformed at 180 min, which was 3.6 times higher than that of pure g-C3N4 powder. This catalyst promotes efficient photocatalytic electron-hole separation for efficient dechlorination by photocatalytic reduction. The samples exhibited high recyclable ability and the dechlorination pathway was clear. The results of Density Functional Theory calculations displayed the TCS dechlorination selectivity has different mechanisms and hydrogen substitution may be more favorable than hydrogen ion in the TCS dechlorination hydrogen transfer process. This work will provide an experimental and theoretical basis for designing high-performance photocatalysts to construct the systems of efficient and safe visible photocatalytic reduction of aromatic chlorinated pollutants, such as TCS in dechlorinated waters.
ABSTRACT
The COVID-19 pandemic has resulted in an increased use of disinfectants worldwide. One of the most popular active ingredients is triclosan (TRC), which is added to personal care products such as soap, wet wipes and dish soap. Negative aspect of TRC in wastewater is its release into the environment, since TRC is not completely removed in WWTPs. In the context of the rapidly increasing concentration of disinfectants in the wastewater influent, the aim of the study was to develop a method for treating wastewater containing TRC. Biological treatment in a sequential batch reactor (SBR) was used, and then the SBR effluent was treated in one of the tertiary processes i.e. ultrafiltration/adsorption/ozonation/ozonation+UV. In the ultrafiltration step, innovative membranes were used, such as membranes prepared from recycled polystyrene (rec-PS) or polyethersulfone mixed with single-walled carbon nanotubes (PES-SWCNT). Adsorption was conducted in fixed-bed columns packed with novel composite adsorbent containing halloysite and single-walled carbon nanotubes. TRC impaired the removal of phosphate and caused the degradation of activated sludge. Phosphate removal in the SBR-2 reactor (wastewater with TRC) decreased throughout the 6 weeks from 48.1 % to 38.1 %;in contrast, for SBR-1 (wastewater without TRC), it increased from 34.3 % to 71.8 %. The phosphate concentration of the effluent exceeded the permissible values, necessitating further treatment. Flocs from SBR-2 were smaller and looser compared to those from the control SBR. Biodegradation of TRC was noted in the 5th week of the operation as methyl TRC was detected in the effluent (0.07 mg/L). In ultrafiltration with PES-SWCNT membrane, phosphate, TRC, and methyl TRC were reduced by 33.7 %, 27.8 %, 36.8 %, respectively. On the other hand, adsorption, ozonation and ozonation+UV processes were highly suitable to treat SBR effluent. The phosphate, TRC and TRC byproducts removal degrees exceeded 90 % both for adsorption in the fixed-bed column as well as the ozonation and ozonation+UV processes.
ABSTRACT
Hygiene is essential to avoid diseases, and this is thanks to daily cleaning and disinfection habits. Currently, there are numerous commercial products containing antimicrobial agents, and although they are efficient in disinfecting, it is still not known the effect of the constant use of these products on human health. In fact, a massive use of disinfectants has been observed due to COVID-19, but the possible adverse effects are not yet known. Triclosan is one of the antimicrobial agents used in cosmetic products, toothpaste, and disinfectants. This compound is an endocrine disruptor, which means it can interfere with hormonal function, with its estrogenic and androgenic activity having already been stated. Even if the use of triclosan is well-regulated, with the maximum allowed concentration in the European Union of 0.3% (m/m), its effects on human health are still uncertain. Studies in animals and humans suggest the possibility of harmful health outcomes, particularly for the reproductive system, and in a less extent for the cardiovascular and thyroid functions. Thus, the purpose of this review was to analyse the possible implications of the massive use of triclosan, mainly on the reproductive and cardiovascular systems and on the thyroid function, both in animals and humans.
Subject(s)
Anti-Infective Agents, Local , COVID-19 , Cardiovascular System , Disinfectants , Endocrine Disruptors , Triclosan , Animals , Anti-Infective Agents, Local/adverse effects , Endocrine Disruptors/toxicity , Humans , Thyroid Gland , Toothpastes , Triclosan/adverse effectsABSTRACT
This review covers publications during the period January 2021 to December 2021 on adverse reactions to antiseptic drugs and disinfectants. Specific agents discussed are alcohols (ethanol, isopropanol), aldehydes (formaldehyde), ethylene oxide, guanidines (chlorhexidine, polyhexamethylene guanidine, and polyhexamethylene biguanidine), benzalkonium compounds, triclosan, povidone-iodine, and sodium hypochlorite. No new data were identified for glutaraldehyde, cetrimide, tosylchloramide, triclocarban, and phenolic compounds. The use of antiseptic drugs and disinfectants has increased considerably since 2020 in various medical and occupational settings, in commerce and gastronomy, as well as in the home, due to their antiviral properties against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) during the still ongoing Coronavirus Disease 2019 (COVID-19) pandemic. Irritant effects on the respiratory system, the skin and eyes were the most common adverse reaction, while the widespread and occasionally excessive use led to increased reports of poisonings as well as of oral misuse of disinfectants, sometimes associated with serious outcomes such as death from methanol intoxication. Eye exposures in children caused by inadvertent exposures due to unsupervised dispensers in public spaces were pointed out as being specifically problematic. Side effects in the eye may also occur in the general population by improper and unprotected use of UV lamps. The need to improve the safe use of disinfectant devices was pointed out in general.
ABSTRACT
Triclosan (TCS), a kind of pharmaceuticals and personal care products (PPCPs), is widely used and has had a large production over years. It is an emerging pollutant in the water environment that has attracted global attention due to its toxic effects on organisms and aquatic ecosystems, and its concentrations in the water environment are expected to increase since the COVID-19 pandemic outbreak. Some researchers found that microbial degradation of TCS is an environmentally sustainable technique that results in the mineralization of large amounts of organic pollutants without toxic by-products. In this review, we focus on the fate of TCS in the water environment, the diversity of TCS-degrading microorganisms, biodegradation pathways and molecular mechanisms, in order to provide a reference for the efficient degradation of TCS and other PPCPs by microorganisms.
ABSTRACT
The widespread use of broad-spectrum antimicrobials has accelerated their entry into aquatic environment, which in turn can adversely affect aquatic organisms and humans, especially in the COVID-19 outbreak and the post-pandemic era. For early detection and intervention of adverse effects, this study develops a new carbon nanoprobe (CNP) that can reveal the adverse effects of trace amount triclosan (TCS), a commonly used broad-spectrum antimicrobial (BSA), through a direct visualization method. CNP has excellent fluorescent properties and strong positive charges, which can be applied as fluorescent indicator and trapped in mitochondria by electrostatic attraction. The highly sensitive responsiveness of CNP to mitochondrial membrane potential ensures the visualization method can be used for monitoring the adverse effects of TCS. The trace amount TCS monitoring is achieved according to the decrease of fluorescence signal in mitochondria and the change of mitochondrial morphological structure from lines to dots. Moreover, monitoring TCS level in aquatic organisms of zebrafish is further realized. Compared with the morphological toxicity test, this visualizing strategy reveals the adverse effects in organisms under low-dose TCS exposure more sensitively. This developed highly sensitive nanoprobe is cruical for direct BSA monitoring and thus prevents the harm of BSA to aquatic organisms and humans.
ABSTRACT
Triclosan (TCS) is an endocrine disrupting chemical which is commonly used as a disinfectant in pharmaceuticals and personal care products (PPCP's). Since early 2020, the worldwide outbreak of COVID-19 has increased the use of PPCP's, so the occurrence and impact of TCS on freshwater lakes should be considered. However, little attention has been given to the effect of TCS on freshwater lakes in China. This study is the first attempt at a risk assessment focusing on the temporal and spatial occurrence of TCS in freshwater lakes in the middle Yangtze River basin. The surface water and sediments of Donghu Lake and Liangzi Lake (Wuhan, Central China) were collected from October 2020 to August 2021. The maximum concentrations of TCS were 466 ng/L and 239 ng/L in surface water, 71 ng/g and 25 ng/g (dry weight) in sediments of Donghu Lake and Liangzi Lake, respectively. Significant temporal and spatial differences of TCS were observed within and between the lakes, with the highest concentrations measured in winter. Furthermore, higher concentrations of TCS were observed in areas that are more impacted by human activities. There was a significant positive correlation between TCS and nitrogen in the surface water. A risk assessment using the risk quotient (RQ) method showed that a potentially high risk (RQ > 1) was found only in surface waters from Donghu Lake, and that the sediments posed a lower risk than the surface waters. These results provide timely data on the temporal and spatial occurrence of TCS in freshwater lakes in China following the outbreak of COVID-19 and demonstrate a possible high risk of exposure to TCS for aquatic biota.
ABSTRACT
Antibacterial filtration materials have been used effectively to control biological pollutants and purify indoor air. This study aimed to assess the antibacterial capability of three fiber filter materials treated with triclosan: glass fiber (GF), non-woven fabric (NF) and chemical fiber (CF). Triclosan was loaded onto the filtration materials by the impregnation method. The triclosan-treated filter materials exhibited antibacterial zones obviously: the average antibacterial bands against E. coli were 11.8 mm (GF), 13.3 mm (NF) and 10.5 mm (CF);against S. albus, they were 25.5 mm (GF), 21.0 mm (NF) and 23.5 mm (CF). The percent reductions of bacteria for the antibacterial air fiber materials treated with triclosan against E. coli were 71.4% (CF) and 62.6% (GF), while the percent reductions against S. albus were 61.3% (NF) and 84.6% (CF). These findings could help to reduce the transmission and threat of epidemic and purify the environment through the use of environmentally friendly antibacterial filter fibers.
ABSTRACT
Antimicrobials like parabens, triclosan (TCS), and triclocarban (TCC) are of public health concern worldwide due to their endocrine-disrupting properties and ability to promote antimicrobial drug resistance in human pathogens. The overall use of antimicrobials presumably has increased during the COVID-19 pandemic, whereas TCS and TCC may have experienced reductions in use due to their recent ban from thousands of over-the-counter (OTC) personal care products by the U.S. Food and Drug Administration (FDA). No quantitative data are available on the use of parabens or the impact the FDA ban had on TCC and TCS. Here, we use wastewater samples (n = 1514) from 10 different communities in Arizona to measure the presence of the six different antimicrobial products (TCS, TCC, and four alkylated parabens [methylparaben (MePb), ethylparaben (EtPb), propylparaben (PrPb), butylparaben (BuPb)]) collected before and during the COVID-19 pandemic using a combination of solid-phase extraction, liquid chromatography/tandem mass spectrometry (LC-MS/MS), and isotope dilution for absolute quantitation. The average mass loadings of all antimicrobials combined (1,431 ± 22 mg/day per 1,000 people) after the onset of the local epidemic (March 2020 - October 2020) were significantly higher (945 ± 62 mg/day per 1,000 people; p < 0.05) than before the pandemic (January 2019 - February 2020). Overall, parabens (∑Pbs = 999 ± 16 mg/day per 1,000 people) were the most used antimicrobials, followed by TCS (117 ± 14 mg/day per 1,000 people) and TCC (117 ± 14 mg/day per 1,000 people). After the 2017 U.S. FDA ban, we found a statistically significant (p < 0.05) reduction in the mass loadings of TCS (-89%) and TCC (-80%) but a rise in paraben use (+72%). Mass flows of 3 of a total of 4 parabens (MePb, EtPb, and PrPb) in wastewater were significantly higher upon the onset of the epidemic locally (p < 0.05). This is the first longitudinal study investigating the use of antimicrobials during the COVID-19 pandemic by employing wastewater-based epidemiology. Whereas an overall increase in the use of antimicrobials was evident from analyzing Arizona wastewater, a notable reduction in the use of TCS and TCC was evident during the pandemic, triggered by the U.S. FDA ban.
Subject(s)
Anti-Infective Agents , COVID-19 , Carbanilides , Triclosan , Anti-Infective Agents/chemistry , Anti-Infective Agents/pharmacology , Arizona/epidemiology , COVID-19/epidemiology , Chromatography, Liquid , Humans , Longitudinal Studies , Pandemics , Parabens , Tandem Mass Spectrometry , United States/epidemiology , United States Food and Drug Administration , Wastewater/chemistryABSTRACT
The usage of triclosan (TCS) has increased with the COVID-19 virus outbreak, causing more TCS were released into wastewater treatment systems. However, the difference in TCS removal pathway and TCS degrading bacteria between nitrification and denitrification systems was still unknown. In this study, batch tests of TCS biodegradation mechanism and DNA stable isotope probing (DNA-SIP) technique were applied to decrypt the different TCS removal pathway and the corresponding degrading taxon between two nitrification and two denitrification systems. The main TCS degradation pathway in both nitrification and denitrification systems were the metabolism of heterotrophic bacteria, only a little TCS was degraded by the co-metabolism of heterotrophic or nitrifying bacteria, and higher NH4+-N or NO3--N concentration contributed to more TCS degradation. Moreover, denitrification system had stronger TCS removal capacity (0.11 and 0.65 mg TCS/g SS) than nitrification system (0.83 and 1.12 mg TCS/g SS). DNA-SIP assay further revealed that active TCS degrading bacteria in both systems belonged to Sphingomonadaceae family. Furthermore, the oligotype TATGCC, TAATCA and GCCCCG of Sphingomonadaceae played important roles in degrading TCS in both systems. Moreover, reactor performance and mixed liquor suspended solids might play important roles in shaping the ecotypes of Sphingomonadaceae, which caused the difference in degrading TCS between nitrification and denitrification systems. This lab-scale research might provide meaningful opportunities for evaluating the scale-up applications, and the TCS degrading bacteria identified in present study might be recommended to be used as bioaugmentation strains in practical engineering.