Assessing environmental quality and health implications of slaughterhouses’ operation within urban residential settings of a developing country

Urban population growth that increases the demand for various private and public land uses has been identified as one of the factors that lead to the current pressure on urban land and conflict of uses in most cities (De Jong et al., 2021). Meanwhile, demand for land in the cities is expected to mount more pressure on the available land as the population grows and urbanisation continues. This is particularly expected in developing nations where population and urbanisation are at an alarming rate without provision for proper planning and lack of concern for anticipated development (Oladehinde et al., 2023). The likes of these urban land use demands are in the form of residential development, industrial growth, commercial land use, recreation demand and other social facilities such as slaughterhouses among others. There is no doubt that conflicts of interest will arise between these urban land use contenders if they are not monitored and proper planning is not implemented (Fienitz, 2023). Of particular interest to this study are slaughterhouses competing with residential structures.

The provision of slaughterhouses as one of neighbourhood required facilities can be traced to the Roman and French civilization of the 15th to 16th centuries (Fayemi and Muchenje, 2013). Slaughterhouses, otherwise known as abattoirs, are places where animals are slaughtered for human consumption and industrial use (Ibrahim et al., 2021). Unlike most developed countries where policies are in place to control slaughterhouses’ operational systems towards sustainability for the environment and healthy living of people, the reverse is the case in most developing countries especially, Nigeria, where control of development is receiving less attention. Systems of operation of most slaughterhouses have been confirmed as a common source of pollution to the immediate environment either directly or indirectly (Ademola, 2019; Oduguwa et al., 2013). Such pollution originating from slaughterhouse operations comes in the form of contaminating the soil and air, as well as polluting the environment through various categories of waste emanating from animal slaughtering activities (Olawuni et al., 2021; Ogunseye et al., 2021; Ogun et al., 2023). This is unquestionably possible in nations where development control enforcement and land use regulation are more of mare policy documentation without serious implementation strategies and willingness for sustainability (Obidegwu et al., 2019; Joachim et al., 2022; Ovuru et al., 2023).

Istifanus and Bwala (2017) postulated that the location of slaughterhouses should be done in a way that the safety of life and property is guaranteed with enough space for parking, waste treatment and free of conflict with other land use competitors. It is expected that there should be adequate provision for the protection of human and animal health as well as protecting the ecosystems. The common practice in many cities of some developing nations is to have slaughterhouses located very close to residential neighbourhood constituting a nuisance to the host communities. The practice is carried out without consideration for abutting land uses, environmental impact on living beings and neglect of global environmental standards. The implications of this development on the nearby residents and the ecosystems have not been adequately studied.

Scholars, such as Mensah and Casadevall (2019), Kuddus et al. (2020), Aliu et al. (2021) and Tonne et al. (2021) posited that factors such as poverty, limited resources due to poor socio-economic status, which characterised the majority of residents of the urban areas of developing nations may have limited the option of moving away from polluted areas like slaughterhouse contaminated environment. Residents, therefore, live with the lethal risks linked with the activities in their neighbourhood even with known pollution effects. Inconsistency in the zoning arrangement of most urban land that allows mixed-use has been ascribed as one of the reasons for the shanty nature of most development in many cities of developing countries (Aliyu and Amadu, 2017; Zhuo et al., 2022). Possible health problems associated with this incompatible land use and its accompanying environmental menace have not been adequately evaluated.

Pollution coming from slaughterhouses in Nigeria has been a source of worry, especially for the immediate environment and stakeholders in environmental management. Various wastes generated through slaughterhouse operations not only constitute a major obstacle to good environmental management but they are also linked to a decline in the environmental quality and the spread of multiple infectious illnesses (Fadare, 2010; Ekpo, 2019; Mozhiarasi and Natarajan, 2022; Khan et al., 2023). The main issue is the health dangers posed to neighbourhood inhabitants by this tragic decision that has not been given due attention. Kefalew and Lami (2021) posited that the amount of effluent created from the blood of a single slaughtered cow dumped straight into the sewer system would be equal to the daily sewage output of 50 individuals. These wastes are largely organic and contain a lot of liquid, fat and suspended solids. The liquid wastes often consist of dissolved solids, blood, stomach contents, undigested feed, urine and wastewater, while the solid wastes typically consist of condemned meat, undigested ingest, bones, horns, hair and aborted foetuses (Ezeoha, 2011). The implication of these waste products was not clearly defined by the study.

Waste disposal in Nigeria just like many developing nations is inappropriately handled by both individual and management authorities (Adeniyi and Afon, 2022). As a result, many open spaces and water bodies have become unattractive. Waste has taken up valuable spaces and smells bad, attracting flies, mosquitoes, mice and other disease vectors and constituting a nuisance to the neighbourhood (Adeniyi et al., 2024). The environment of most slaughterhouses is a typical example of sources of waste that pose a very serious threat to the environment of most cities such as Ede, Nigeria. Slaughterhouses are typically situated close to water bodies or areas with high water tables because of their high water requirements (Badejoba, 2014). This allows them to have unrestricted access to water for processing their products (Akanni et al., 2019). The butchered meats are rinsed in the polluted water and the effluents from these slaughterhouses are released straight into streams and rivers without any sort of treatment (Birhanu and Menda, 2017; Adebowale, 2019; Adzawla et al., 2019). This practice could result in the spread of pathogens to people which can lead to illnesses of various types (Fayemi and Muchenje, 2013; Bandaw and Herago, 2017).

Efforts have been made by scholars through research on slaughterhouse operation in proximity to residential neighbourhood. Some of these studies focus on different problems the slaughterhouses operations and the solutions proffered are not holistic to address the issue of this land use conflict between urban land uses such as human habitats. Bello and Oyedemi (2009) investigated the effect of the management of abattoirs in the residential neighbourhood of Ogbomoso, Nigeria. Though the study identified pollution of surface water as the effect on the residents, implications on surrounding soil were not within the scope of the study. Similarly, Daramola and Olowoporoku (2017) and Adonu (2017) researched the effect of slaughterhouses in residential areas and concentrated on the impact on the health of the residents. Effects on other physical environment aside from water were not adequately reported. Istifanus and Bwala (2017), Ogunkeye et al. (2021) contributions were on waste management practices in abattoirs of semi-city, information obtained cannot be used to determine operation in urban areas. Kefalew and Lami (2021) delve into potential of abattoir waste for biogas and bio-fertilizer, whereas Mozhiarasi and Natarajan (2022) worked on the possibility of converting waste generated from abattoirs to generation of renewable energy. The two studies’ interest was not in the damages caused by this development to humans and the environment. They both investigated the potentials of waste emanating from abattoirs. It can be understood from the foregoing that most previous studies did not extensively discuss the pollution and health effects of abattoirs with due consideration for human habitat. Hence, the task before the current study.

This study examines the reasons and implications of mixed land use between slaughterhouses and residential buildings. The study also investigates the type of waste generated from the abattoirs, the extent of noise pollution generated and implications of the operation method on water and soil in the surrounding environment. Also determined are the health implications on the residents living within a distance from the abattoirs and general impacts on the environment. Based on the above, this study will attempt to provide answers to the following questions:

This study was conducted in Ede, southwest Nigeria, located between latitudes 7° 41’N and 7° 56’N, and longitudes 4° 27’E and 4° 34’E (Figure 1). It comprises of two Local Government Areas; Ede North and Ede South with a total land area of about 334 square metres (334 m²) (Adeniyi et al., 2022). The land use ranges from residential to commercial, industrial, circulation open space as well as recreation (Olayiwola et al., 2010). Based on the most recent national headcount, Ede has a total population of 159, 307 people [National Population Commission of Nigeria (NPC), 2006].

Therefore, based on the official 3% annual growth rate for urban centres in Nigeria, the population of Ede in 2023 was estimated to be 263,310 [National Bureau of Statistics (NBS), 2016]. The population projection was calculated using the formula: P (1 + r/n), where: P is the population of the base year: base year = 2006; n is the number of years between the base year and the study year (17 years). The method has been used by Adeniyi et al. (2023a, 2023b). The major and, perhaps, the most significant factor responsible for the present-day population growth in the study area is migration initiated by the creation of Osun State in August, 1991 and existence of two private Universities, one Federal Polytechnic and two private colleges of Education (Adeniyi et al., 2022). This study focused on Ede Township (excluding all other neighbouring rural settlements) for several reasons. Among the reasons for the limitation of the study to the township is level of urbanisation which is more obvious in the township than the rural areas. Therefore, the effects of this development are yet to be felt in the suburb of Ede. Similarly, since the target for the location of any investment is to maximise profit through more demand, these slaughterhouses are concentrated in the city where market are available.

Like any other urban in Nigeria, Ede witnessing major environmental changes prompted by population growth. This has led to, and continues to impact on the physical expansion of the town. Consequently, urban problems of various forms in varied convolutions emerge. As expected, such expansion is associated with some environmental consequences prominent of which is conflict of land uses calling for proper attention. One of the prominent activities that grows along with the city expansion is development of urban facilities especially slaughterhouses otherwise known as abattoirs. Interest of this study is development of this facility within people’s habitat and associated pollution of various types constituting nuisance to nearby residents. Environmental implication of this development in the urban settings is the target of this study.

To obtain necessary information needed for the study, data was obtained from primary and secondary source. The flow chart of how data used was obtained and analysed and is summarised in Figure 2. To achieve this, the multi-stage method was used to obtain the data used. First stage was the identification of the available slaughterhouses and their locations within the town. Second stage was the selection of samples among the identified slaughterhouses for the survey. The next stage was the identification of the residential structures within a stipulated radial. The last stage was collection of samples for actual measurement of pollution observed on natural resources attributed to abattoir operations and administration of questionnaires on the residents of the area whose building were at the stipulated distance from the slaughterhouses. The 16 abattoirs identified that spread across the city are the sample population for this study.

They are found to be located along water ways due the volume of water needed for butchery activity. Only 8 of the abattoirs accounts for 50% of the total were randomly chosen for this research. The sampled size is considered adequate for the study when compared with the percentages used by previous studies of similar nature. Selected abattoirs include Oke-Gada, Sabo, Cottage, Sawmill Allahu-Lateef and Alusekere; others are Ogberin, Mapo and Ojoro slaughterhouses. The slaughterhouses selected and the number of questionnaires administered in each are presented in Table 1.

Waste disposal and management practices of the abattoirs were investigated. Also examined are the levels of noise pollution from these slaughterhouses as well as measurement of the impact of waste generated from this activity on the soil around the neighbourhood. To determine effects on the residents, residential structures within 1,000-meter radius of a selected abattoir were chosen for the survey and questionnaires were administered on the residents. This radial distance is greater than 500 meters used by Daramola and Olowoporoku (2017) and the coverage is more than 100 meters radial distance earlier considered by Bello and Oyedemi (2009) in a similar study. Also used for this study is personal observation by the researchers. The owners of the buildings or their representatives were the target of the survey in each of the selected residential building. Investigated from the residents are the age of their buildings compared to the existence of slaughterhouses in the area, effects of abattoirs operation on the residents and types of pollution transmitted. Through this and proper monitoring, a total of 141 questionnaires were administered and recovered. A number of questionnaires administered in each area depends on the size of abattoir and volume of the building that fall within the target coverage earlier stipulated. Other investigations carried out on the study are how waste generated as a result of this development is disposed, extend of damages done through the noise, to the air and soil in the area attributed to the activities of abattoir operations. Data collected was analysed with descriptive and inferential statistical methods. Descriptive analytical methods used for data presentation are percentages, tabulations and figures. Inferential analytical tool used to determine the significant environmental related diseases affecting the residents is one way ANOVA.

This section presents results of investigation made on various slaughterhouses investigated and findings are presented under various sub-headings. These include position of the slaughterhouses in relation to the city centre, analysis and compare of time of existence between the slaughterhouses and residential structures, types of waste generated and methods of waste disposal.

To substantiate the existence of the slaughterhouses within the residential area, the study investigated the exact location of the selected of abattoirs in the city using a Geographical Information System. The intention is to determine the radius of the slaughterhouses from the centre of the city. Figure 3 shows the location of the facility on the map of the study area. It can be understood from the map that all the slaughterhouses are located along water bodies because of water usage requirements. It is also understandable from Figure 2 that all the slaughterhouses are still within the built-up area of the city where people reside.

The study further investigated the actual distance of the slaughterhouses from the centre of the city. The palace which is the traditional headquarter of the town based on the tradition of the study area (Umoru-Oke, 2010) was chosen as the centre for this study. The measurement was obtained with the use of Geographical Information System. The result obtained, summarised in Table 2, showed that the slaughterhouse with the highest distance from the city centre is Sawmil Alau-lateef with the shortest road distance of 4,498.5 metres and straight-line distance of 3,998.5 metres. The abattoir with the shortest distance from the centre of the city is Sabo, with shortest road distance of 1,730.9 metres and straight-line distance of 1,326.4 metres. It can be established that the location of these service providers is still a threat to the health of the people in urban areas when observing the extent of the area covered by residential buildings in the town.

Further study revealed the distance of the slaughterhouses from the nearest building. Information obtained, as shown in Table 2, showed that Alusekere slaughterhouse had the shortest distance from the nearest residential building with 60.8 metres. The slaughterhouse with the highest distance to the nearest building was Sabo with 350.7 metres. It can be established from the study that all the slaughterhouses surveyed are less than 500 metres, the minimum distance that is considered to be the minimum from a residential building for such a facility (Musa et al., 2023; Benjamin et al., 2024).

Further investigation established that most of the slaughterhouses were built before the development of the majority of the residential buildings in the area. About 73% of the residential buildings surveyed in the city are in this category. Only 27% of the buildings were constructed before the establishment of the abattoirs in their area. This has implications in planning administration especially in the environment where zoning of land uses is not giving priority. It is also implicated that these slaughterhouses may have considered a distance from the existing living houses at the time of their establishment. Therefore, the problem may have been caused by ineffective zoning arrangement that can be blamed on ineffective physical planning control in the study area. Meanwhile, further investigation shows that neither the slaughterhouses under study, nor the residential buildings obtained building approval permits from the local government planning authority responsible for such in their various locations. The majority of the slaughterhouses has started operations under temporary structures constructed of plank materials which were later converted to permanent structures. This can also be attributed to ineffective land use policies characterised most cities in sub-Sahara Africa.

To have information on the people living within the stipulated 1,000 metres radius of the slaughterhouses, socioeconomic characteristics of the residents was investigated and summary of finding is presented in Table 3. It can be established that the majority of the respondents are aged, above the retirement age of 60 years stipulated by the law of the study area. This category of residents is considered as economy inactive citizen according to the law of the nation. Aged accounts for 57.5% of the respondents. Adult of between the ages of 40 and 60 years are 26.2% while youth (20–40 years) are only 16.3% of the people living within 1–1,000 metres radius of the abattoirs in the study area. Equally sought is the gender of the respondents.

Information obtained shows that male was the majority of the people that owned buildings within a close range to the slaughterhouses in the study area. This can be established with 66.7% of the respondents claiming to be male while female represents 33.3%. The fact that head of the family was the target of the survey might have responsible for the result obtained.

Related to gender is the marital status of the respondents. This study finding shows that married were the majority, accounts for 60.3%, widow represents 19.9% and divorced are 13.4%, while single accounts for only 6.4% of the total. This indicates that the majority of the residents are married who are responsible for their family members’ need including well-being and safety of live and security. Further study from summary in Table 3 established that the majority of the respondents did not attain formal education as highest figure of 38.3% falls into this category among the respondents. Only 33.3% and 25.5% of the respondents attained primary and secondary education, respectively. This might influence the nature of occupations sough as well as the low-income status of the respondents. Thus, this might also be responsible for low level of awareness of the severity and sensitivity to the effects of the environmental pollution generated from the abattoir activities. Similarly, the study further established that trading was the most important occupation engaged in by the residents. It accounts for 47.5%, and followed by artisan that accounts for 32%. Only few respondents (1.4%) engaged in civil service which required more education background.

Further investigation showed that the majority of the respondents earned less than ₦30,000 in a month which is less than one dollar per day. The residents under this category account for 48.2% of the respondents. However, only 24.1% of the respondents earned above ₦50,000 monthly. It connotes that the majority interviewed are living below global poverty line of $1.90 per day, based on Aguilar et al. (2021) submission. It can be established that low socio-economic profiles of the residents within the abattoir areas of urban settings may have responsible for continuous living in the area despite the environmental challenges that might be experienced.

Also investigated is the type of waste products generated from the abattoirs in the area. Information obtained showed that two types of waste are produced as a result of abattoirs operation in the study area. These include solid and liquid wastes. Solid waste generated in the area includes animal dung, carcass and animal food remnants. They, respectively, account for 39%, 18% and 13% of the total waste generated in the slaughterhouses under investigation. Blood is the liquid waste produced in the area represents 30% of the total waste. It can be established that animal dung followed by blood are respectively the most important and second most important waste components generated in the selected slaughterhouses in the study area. Summary of the waste generated is as presented in Figure 4. Thus, these categories of waste if not managed properly can negatively impact the health of the residents and the entire living organisms in the area. Further study showed that, disposal into open space was the common waste disposal method adopted by all the slaughterhouse operators, accounts for 42% of the disposal practices. As summarised in Table 4, 32% of the operators disposed waste into the water body, 15% burned waste, whereas only 4% disposed outside the abattoir’s premises. It can be established that most of the methods adopted by abattoir operators to dispose waste in the study area are not environment-friendly and could be a source of threat to the health of the people living closer to this facility and a threat to the environment in general.

Ecosystems require a mutual understanding of animals, plants and the physical environment of which noise, soil, air and water were included. The study further looked into the environmental distortion to the natural environment emanating from slaughterhouses operations within residential areas. The impacts inform of noise level and implications on the soil in the nearby areas were particularly investigated. The study established that the noise pollution level around the slaughterhouses area measured using noise dosimeter was high. Results of the test conducted on noise pollution around most of the selected slaughterhouses, which is summarised in Table 5, show that Alusekere slaughterhouse produced the highest effect with 107.8 dB. This was followed by Cottage with 82.5 dB. Others are Sabo (79.2 dB), Oke-Gada (74.5 dB), Mapo (63.1 dB), Sawmill (62.7 dB) Ogberin (59.2 dB) and Ojoro (57.8 dB). The measured noise levels showed explicitly that noises generating from each of the abattoirs are higher than the World Health Organisation (WHO) standard of 55 dB recommends as normal noise level limit for outdoor noise in residential areas (Jarosińska et al., 2018; Quartey et al., 2021). Implications of this high noise level according to Chen et al. (2020), and Krittanawong et al. (2023) are hearing loss, sleep disorder, cardiovascular disease and hypertension.

Physiochemical property analysis of the soil in the areas around the slaughterhouses was conducted. This was to determine the level of the impact of the slaughterhouse activities on the nutrient contents and characteristics the soil within the study area. To achieve this, eight randomly selected soil samples were collected at the depth of 1–30 cm and sundried. The collected soil samples were taken to the Department of Agronomy, University of Ibadan, for analysis. Sample 1 was collected from Oke-Gada, Sample 2 from Sabo abattoir, Sample 3 from Cottage abattoir and Samples 4 and 5 from Sawmill and Alusekere abattoirs, respectively. Mapo, Ogberin and Ojoro were responsible for samples 6,7 and 8, respectively. The soil samples considered for analysis are refuse site waste and automobile waste. Six elements detected are: PH, lead, cadmium (Cd), iron (Fe), zinc (Zn) and soil nitrates. The results obtained when compared to Nigeria’s Federal Environmental Protection Agency (FEPA) standards show that most of the slaughterhouses, except Sample 8, have an acidic soil with PH greater than 7. Also, all other organic compounds are extremely high compared to Nigerian FEPA and WHO standards (see Table 6). Apart from reducing the nutrient of soil, this can cause heavy contamination of underground water in the surrounding environment. It can also contaminate well water around the abattoirs area causing varying degrees of diseases on consumption of flowing water. Since most of the abattoirs are sited very close to water bodies, degree of soil acidity can also be a source of danger to aquatic animals who may find the high acidity unbearable for living. Similarly, high values of acidity in soil around the slaughterhouses especially pH can also negatively influence the suitability of soil for growing plants. This is particularly dangerous in a developing country where climate change has necessitated the propagation of irrigation farming in the lowlands and backyard farming around the plain areas. This farming practice is known as FADAMA project in Nigeria (Oyebode and Akinbile, 2021).

Very important to the study is the health implication of location of abattoirs very close to residential areas of the study area. As presented in Figure 5, environmental-related sickness is one of the major impacts felt by the residents, with 44% of the respondents affected. Odour from the abattoirs was considered unfriendly to health by 40% of the residents, whereas 22% expressed unbearable environmental pollution as health threatening impact felt due to closeness to abattoir. Other effects experienced by the residents in the abattoir area are attraction of flies, contamination with water and blockage of drainage. It should be noted that these are the effects that can result to environmental disaster in the area. The results of one-way ANOVA computed on the severity of health effects of environmental pollution show that all the pollution-related diseases varied significantly across the residents with F values of 15.642, 12.165, 44.460, 30.414, 66.710 and 47.883 and p values of < 0.01. This implies that the severity of sickness, pollution, odour, contaminated water, blockage of drainage and high number of flies vary significantly across the abattoir areas.

This study assesses the environmental impacts of abattoir’s activities within the residential areas of the suburban of Ede Town. The study showed that the locations of most of the slaughterhouses are very close to residential buildings than the minimum standard expected of such facility. Similar results were obtained by Odugunwa (2013), Daramola and Olowoporoku (2017) and Ademola (2019). The study established that most of the abattoirs existed before the development of most of the residential buildings in the area. This implies that distance from where people resided may have been considered before the slaughterhouses were established in their present locations. Therefore, none of the abattoirs was constructed to meet hygienic standard as recommended by the national and international environmental regulatory organisation. The same observation was reported by Annan-Prah et al. (2012). It was further established that approval for development of slaughterhouses was not obtained by the operators of this facility before construction. Lack of land use zoning plan and ordinance to back it may have responsible for the conflict of use between the abattoirs and human residential development. The study established that majority of residents are not only socially unstable, but also not economically sustainable. It was also revealed by the study that most of the wastes generated from the abattoirs are organic in natures which are disposed into open spaces especially at the bank of running water. This category of waste if adequately exploited could be used as source of wealth or resources for other sectors and thereby enhancing resources conservation and promoting circular economy. This substantiates Khan et al. (2023) that potential of wastes generated from abattoirs are underused.

Similarly, this study established that both the noise and soil around the abattoirs have been polluted making the noise decibel (ԀВ) greater than the WHO recommended level. Such noise pollution was equally reported by Conrad and Enyonam (2011) and Istifanus and Bwala (2017) as a common problem of abattoir located within residential neighbourhood. The study also observed soil pollution, revealing that it contained PH levels and lead concentrations with acidic content exceeding the safety recommendations for table water set by the Nigerian FEPA and WHO. This is what Bello and Oyedemi (2009) and Adonu et al. (2017) concluded that negatively affect the quality of well water and other surface water near abattoir sites making the quality of the environment deteriorating. Thus, this constitutes threat to the residents. It may have responsible for the common environmental health-related sicknesses that was reported by the majority of the residents of the area. The finding affirms the studies such as Bello and Oyedemi (2009), Daramola and Olowoporoku (2017), Adonu et al. (2017) and Ogunseye et al. (2021), which indicate that residents living near of abattoir areas are at risk of environmental health-related sickness if the area is not properly managed.

The study concluded that sitting abattoir within residential area is very detrimental to the environment which could eventually impact the wellbeing of the residents living around the facility and the future generation. This is particularly against the principle of sustainable urbanisation of managing cities in a way that minimises environmental impact and promotes social equity and economic development. To protect the environment and making urban living conditions more adorable, resilient and sustainable for the current and future generations, the following recommendation are proffer. There is the need to urgently encourage and legalised zoning of urban and rural land so that land of incompatible use will be prevented and social conflict will be prevented. It is urgently required that all the slaughterhouses in the study area be relocated into a new location free of residential buildings with proper monitoring by government agencies. This is particularly essential to sustain urban economic, increase property values and incorporate innovative urban design principles. Proper management of the environment especially waste from abattoirs must be backed by laws and regulations followed by full implementation and regular monitoring. Through this, a goal of millennium development goal which is an essential part of ensuring environmental sustainability will be achieved. This study also recommended that abattoir operators should be educated on the economic and environmental importance of waste generated from the abattoirs and the needs for proper management in an environment-friendly method that is in conformity with the global accepted practice. This could also reduce conflict between the operators of slaughterhouses and residents. There is the need for a further study that will review environmental laws and regulations that is guiding the management of waste generated from abattoir operations which the current study could not delve into due to scope of the research.

Statements and Declarations.

Funding: The authors declare that no funds, grants or other support were received during the preparation of this manuscript.

Data availability: The data sets used or analysed during the current study are available from the corresponding author upon reasonable request.

Competing Interest: The authors have no relevant financial or non-financial interests to disclose.

Ethical Statement: All authors have read, understood and have complied as applicable with the statement on “Ethical responsibilities of Authors” as found in the Instructions for Authors.