1. Introduction
With rising technological developments in society, new possibilities have occurred and that could simplify our daily life and provide more efficient services or production processes. Digitalization has allowed ‘‘smart’’ (Zheng et al., 2019) to become the epicentre of already ongoing technological developments. In fact, IoT technologies are nowadays assumed to be one of the key pillars of the fourth industrial revolution due to significant potential in innovations and useful benefits for the population. On the other side, each development utilizes limited resources leaving behind different environmental footprints, (Li et al., 2020a), especially different kinds of pollutants, (Zeinalnezhad et al., 2020). Internet of things (IoT) based technologies bring a completely new perspective on the further progress of various fields, such as for instance in engineering, (Zaidan and Zaidan, 2020), agriculture (Farooq et al., 2020), or medicine (Salagare and Prasad, 2020), and in other fields that have not been explored yet. Some potential application areas in IoT technologies are still unknown or insufficiently clear on how to approach them which is an evident indication that more intense research activity should be conducted in this challenging field towards new and important potential benefits for society. Therefore, the relevance and importance of IoT technologies in future terms are more than clear and should play an important role.
The rise of IoT technologies is currently intense and according to projections for the next 10 years, over 125 ·109 IoT devices are expected to be connected, (Techradar, 2019). The expected investments in IoT technologies are also high with expectations being over 120 ·109 USD by 2021, with a compound annual growth rate of about 7.3%, (Forbes, 2018). The general present market structure of IoT technologies is presented in Fig. 1 , where it is evident that the majority of the market is focused on smart cities and industrial IoT.
If recent projects in IoT technologies are being analysed than most of them are in the field of smart cities and industrial IoT. Other significant potentials are connected buildings, connected cars and energy segments (Forbes, 2018), but lower than the first mentioned fields. It is also found that the most rising trend in the number of IoT projects currently is as expected in smart cities, connected health and smart supply chain segments, with an annual rise over 30% in the EU and USA. Industrial IoT, connected cars and agriculture segments has recorded a decrease in the number of realized projects, i.e. over 25% in the USA and EU, (Forbes, 2018). From a perspective of high upcoming population pressure on cities and because a population of almost 11 ·109 is expected by the end of the century (Pewresearch, 2019), the smart city concept could become a vital one to allow for a normal operation of highly populated cities.
In order to support the rapid technical development of IoT technologies, as well as novel potential applications areas, specific technical issues would need to be resolved, (Techradar, 2019). One of the main issues is associated with the development of different tools for the monitoring of network operations (Kakkavas et al., 2020), then issues with security tools and their management, (Conti et al., 2020), issues with software bugs, demanding maintenance of IoT networks, and finally security issues related to IoT networks, (Almusaylim et al., 2020). The important problem linked with the efficient implementation of IoT technologies is linked with the available speed and coverage of wireless networks (Wi-Fi), where expectations are high due to noticeable increases in Wi-Fi network coverage in the period of 2017-2022 as well as increases in Wi-Fi speed Fig. 2 . In a global sense, increases in Wi-Fi speed are expected for more than a factor of two, i.e. from about 24 Mbps to more than 54 Mbps. The most intense increase in Wi-Fi speed is expected in the Asian region, (Zdnet, 2018).
The lowest Wi-Fi speed is noticeable in the Latin America and Middle East&Africa regions, which are an indication of potential problems for the efficient implementation of IoT products or novel more advanced upcoming technologies.
An increased implementation of IoT technologies would lead to a more intense utilization of fossil technologies to ensure the necessary energy supply for IoT production lines. The production of electronic equipment is causing potentially unbalanced waste of limited metals and resources in general, which could become a critical issue in the long run. Unfortunately, the recycling rate of electronic waste is low and currently in the amount of about 20% (Thebalancesmb, 2020) which makes matters questionable regarding the available resource capacity to produce IoT products when taking into accounts the rising market demands. The production of electronic gadgets has led to the consumption of various chemicals, water and finally fossil fuels that have all left environmental impacts. As already tackled, different metals are also being used to produce electronics such as copper, silver, gold, palladium etc. One of the major issues is the led content in e-waste and its severe impact to the environment. Recycling in the previous sense is very important, where the present recycling rate of electronic equipment is certainly not sufficient and must be increased. Globally, the annual rise of the recycling rate ranges from about 4% to 5% (Thebalancesmb, 2020). The legislation related to the e-waste is one of the main drawbacks since more than 50% of world population is still not well covered with proper legislation related to e-waste, (Globalewaste, 2017), which is preventing the further development of e-waste facilities. The market value of raw materials from e-waste is estimated to be more than 50·109 Euros, (Globalewaste, 2017). Certainly, more strategic and targeted actions are needed in the e-waste issue to secure a more balanced and sustainable development of IoT technologies. Overall, the annual generation of e-waste is more than 44·109 metric tonnes, which is equivalent to more than 6 kg per inhabitant annually, (Globalewaste, 2017). A potential exists and must be better utilized to ensure a sufficient quantity of valuable raw resources.
It should be highlighted that there is no doubt in what IoT technologies would bring to the table, such as various useful benefits to society and an overall improvement in life quality. Each technology has specific issues and drawbacks that need to be detected and closely investigated on time, since IoT technologies have the potential to change our lives and habits. Several important facts need to be emphasized when addressing IoT technologies to be able to understand the long-term effects associated with the fast development of IoT:
The main point of the above raised issues is not to indicate and create a negative attitude towards IoT technologies but to carefully analyze the overall aspects in order to secure a smart and sustainable development of IoT technologies, which are a valuable opportunity for humanity.