1. Introduction

The globalization and modern lifestyle require high utilization of technologies for long-distance communication, independent of the location on which humans might be encountered. To attend to this need, telecommunication companies spread its service throughout the world, building structures for implementing transmitting devices (antennas). Currently, it is estimated that there are 97.296 mobile telephone stations in Brazil (Agência Nacional de Telecomunicações, 2020; Teleco – Inteligência em Telecomunicações, 2020), and 1,018,132 antennas located on top of the structures in the USA (National Institute for Occupational Safety and Health, 2004). Such antennas are normally mounted on roof perimeters of existing buildings or on telecommunication towers. The towers may be of several types and range in height from 100 to 2,150 feet (from 30.5 to 655 m) or more: monopole (from 30.5 to 61 m); self-supporting (30.5 to 122 m); and guyed (30.5-655 m).

As the number of telecommunication towers increase, so will the number of workers in such a highly specialized construction and maintenance work. The new towers are built in pieces and mounted onsite through the use of cranes. After towers are erected, maintenance activities include reinforcing the structure, painting the steel structure, changing bulbs, and troubleshooting malfunctioning equipment, upgrading antennas, and installing new antennas on existing towers (National Institute for Occupational Safety and Health, 2004). The preferred method for accessing telecommunication towers is to use fixed ladders with attached climbing devices, ensuring protection during ascent and descent of the structure. However, as materials are sometimes bulky or heavy, they are normally hoisted to the height where they will be installed (Occupational Safety and Health Administration, 2014).

The OSHA estimation is that in the USA alone, there are from 10,000 to 29,000 workers involved in construction and maintenance of telecommunication towers, including communications workers, painters, steel erectors, and electrical and electronic equipment repairers. All of them are normally exposed to various occupational safety and health risks, including falls, structural collapses, struck-by hazards, worker fatigue, radio frequency exposure, inclement weather (including extreme heat and cold), electrical, and cuts and lacerations due to the use of sharp, heavy tools and materials. Therefore, it is essential that these maintenance workers are physically fit, comfortable working at height, have a responsible attitude, able to communicate clearly with other personnel, aware of their own limitations, fully aware of the hazards related to the machinery which they are required to maintain, that are properly instructed and trained, familiar with working at height procedures, fully aware of manufacturers instruction manual, familiar with the construction site and associate hazards, and trained and competent to previously inspect and correctly use necessary personal protective equipment (Tower Crane Interest Group, 2008).

Although the real effect of the exposure to electromagnetic fields is still not very well understood, traditionally used antennas may exceed reference levels for workers and the general public when working in close vicinity (Alanko et al., 2008). With the development and implementation of new technologies such as 5G networks, the public interest increased (Wiart et al., 2019) as such transmitting devices could have a greater impact on health. This will therefore pose new challenges on the evaluation and management of exposure to electromagnetic fields. Nevertheless, the highest occupational risk for construction and maintenance workers continues to be safety-related.

The data show that there is a high risk of accidents associated with telecommunications towers work. The average annual ratio of injuries to fatalities in telecommunications towers for the years from 2006 to 2017 was 8.4 (Occupational Safety and Health Administration, 2018). Most of the identified fatal accidents included falls from height, tower collapses and electrocutions, with the following contributing factors: hoist failure; truck-crane failure; inadequate fall protection; failure to attach the lanyard to the tower; terminal devices on the lanyard that are not compatible with tower components; attachment of lanyard to unstable tower components; failure to ride the line under prescribed conditions; inadequate worker training; and potential fatigue and repetitive strain (National Institute for Occupational Safety and Health, 2004). All of the mentioned accidents at work could have been prevented by applying adequate risk management measures, however, there is a high number of electrical and telecommunication installation companies which don’t implement safety and health management systems (Vila et al., 2020).

Due to high risks to which maintenance workers of telecommunication towers are exposed, and a low number of studies in relation to occupational risks management, the aim of this study was to conduct a set of case studies in order to identify, analyze and evaluate risks and give suggestions on control measures which should be applied in order to eliminate or reduce the risks of accidents.

2. Materials and methods

The study was conducted in Recife, Brazil, on workers dealing with the maintenance of telecommunication towers - installing antennas. In total, three teams from different companies participated in the study, each team having three workers (totalizing a number of nine workers): the supervisor; the technician; and the support worker. The types, weight and dimensions of installed antennas were illustrated in table 1.

Table 1

Antenna characteristics.

The fluxogram of a working day with activities usually performed by teams participating in the maintenance of telecommunication antennas was illustrated in Figure 1.

Figure 1
Fluxogram of a working day and activities.

For the purpose of this study, it was decided to use the directives given by ISO 31000 (Associação Brasileira de Normas Técnicas, 2009) for conducting the risk assessment process, which was divided into: risk identification; risk analysis and risk evaluation. Afterward, suggestions were given in order to suggest possible measures for an effective risk control.

2.1. Risk identification

For identification of risks of accidents, it was decided to structure two questionnaires and one checklist.

The Questionnaire 1 (enclosed as Appendix A) was developed in order to evaluate maintenance workers. The questionnaire had 26 questions on general information of workers: names, function, weight and height, experience in the working activity, safety trainings which they undertook, and others.

The Questionnaire 2 (enclosed as Appendix B) was developed in order to evaluate employers. The questionnaire had 15 questions on general information of the company: the number of workers, working period, safety procedures and trainings in use, the supervision of workers, accidents which occurred in the past, and others.

The Checklist (enclosed as Appendix C) was used in order to effectively identify sources of safety risks associated with the maintenance process and the equipment in use during the working activity. The checklist was structured according to the methodology Barkokebas (Barkokébas Junior et al., 2004), including a series of questions based on items from current Brazilian norms, adding answers for each item: Conform (C), Non-Conform (NC), Not Applicable (NA), and when necessary, giving additional observations.

For the purpose of this study, a checklist was structured containing 95 items from four Brazilian regulatory norms (NR) and one technical norm (NBR): NR 6 on Personal Protective Equipment with 9 questions (Escola Nacional da Inspeção do Trabalho, 2018a); NR 7 on the Program of medical control of occupational health with 6 questions (Escola Nacional da Inspeção do Trabalho, 2018b); NR 10 on Safety in services related to electrical installations with 7 questions (Escola Nacional da Inspeção do Trabalho, 2016a); NR 35 on Working at heights with 67 questions (Escola Nacional da Inspeção do Trabalho, 2016b); NBR 5419 (Associação Brasileira de Normas Técnicas, 2001) on Protection of structures against lightning strikes with 6 questions.

2.2. Risk analysis and evaluation

After identification, the risks were analyzed and evaluated by using the Hazard Rating Number (HRN) as illustrated in Table 2. The risks were quantified by the Risk Classification (RC), which was calculated by multiplying the degree of severity (DS), the exposure frequency (EF), the probability of damage occurring (PD), and the number of people at risk (NP).

Table 2

Hazard Rating Number.

2.3. Risk control

Suggestions on risk control measures were applied for all safety risks identified, analyzed and evaluated during the risk assessment process. For this purpose, it was decided to follow the hierarchy of risk control, a widely accepted concept followed by main occupational safety and health authorities worldwide, including ISO and OHSAS (Barkokébas Junior et al., 2020). First were given suggestions on how the risks could be eliminated, then giving possible preventive measures (substitution and engineering measures), and finally giving possible reduction measures (administrative and Personal Protective Equipment (PPE)).

3 Results and discussion

The analyzed telecommunication towers were located in different parts of the city and sometimes in the nearby county area. As the towers were randomly distributed, workers often visit some locations and towers for the first time. As workers are not familiar with the specifics of the location and towers, it is therefore needed to well plan and organize the activity prior to conducting any maintenance work. Additionally, support from local persons would benefit to improving occupational safety and health and even shortening the working period.

3.1. Risk identification

Through the participation of nine maintenance workers, it was realized that although each team consisted of a supervisor, a technician, and a support-worker, they all participated in all phases of the maintenance of antennas, being therefore exposed to same occupational risks. All participants had a high-school educational level. All of the participants reported to have been trained for working at heights. Main results from the questionnaire 1 and 2 were illustrated in Table 3.

Table 3

Main results from the questionnaires 1 and 2.

* SD = Standard Deviation.

As shown in Table 3, supervisors were the most experienced from the team, with 11.33±1.53 years of experience. The technician had 6.67±1.53, while the support-worker had a mean of 4 years of experience. As it could be noticed from the Table 3, although safety and health measures were applied poorly, with no risk analysis, no inspections or existence of PPE checklist, it could be noticed that there were only few minor registered accidents in company three, while other two companies didn’t have any cases of accidents.

The results from the checklist, as one of the methods used for risk identification, were illustrated in Figure 2. There were 76 items in non-conformity (80% of the checklist): the items in relation with PPE; Electrical installations; and most of the questions related to working at heights. There were 19 items in conformity (20% of the checklist): items related to the medical control; and some items related to working at heights.

Figure 2
Checklist results.

The items from the section of “NR6 - Personal Protective Equipment (PPE)” were all in non-conformity didn’t have required characteristics, or were not available for using. The occupational health certificates required by the “NR7 - Medical control” were all in conformity.

All items required by the “NR10 - Electrical safety” were in non-conformity as: no one undertook trainings on electrical safety, including the identification and evaluation of risks and precautions; no trainings for first aid assistance; the risk analysis was never conducted prior to working activities. Maintenance workers didn’t have access to circuit breakers for by de-energizing accessed parts.

The items from “NBR 5419 on Protection of structures against lightning strikes” (Associação Brasileira de Normas Técnicas, 2001) were all in non-conformity: the metallic structure of the roof was not interconnected with the catchment subsystem; the cables from the catchment subsystem were not installed in the perimeter of the system, nor connected to the descending subsystem; the subsystem was not connected to the grounding subsystem; the grounding electrodes were not at least 1.0 meter away from the building's external walls.

Most of items from the checklist (67 items, 70.52%) were in relation to the “NR 35 - Working at heights”. From those 67 items, 79.1% were in non-conformity, while only 20.9% were in conformity. The non-conformity for all three companies was in relation to: no prior studies on how the work at height is carried-out; no supervision if adequate control measures for working at height have been implemented; no prior authorization was issued and no procedures for working at height; no training for carrying work at heights; workers were not previously trained and approved in theoretical and practical training for working at heights with a workload of at least 8 hours; the workers were not trained how to use PPE for working at heights; no trainings for first aid assistance. The risk analysis didn’t consider: the location on which the service was conducted; the signalization; anchorage points; meteorological conditions; the inspection of the utilization of collective and personal protective equipment; the risk of falling objects; communication systems; if the worker was connected to the anchorage system throughout the period of working at heights; availability of an emergency team; among other questions. The conformity was in relation to: periodic biennial training in procedures, conditions and work operations with a workload of at least 8 hours; the periodic health assessment of those working at heights; the equipment for working at heights; the items in relation to the safety harness for working at heights and its correct use.

3.2. Risk analysis and evaluation

The identified risks of accidents with its classification according to the HRN = LO x FE x DPH x NP, were illustrated in Table 4. The risks of falling objects and falls from height were classified as “high”, electrocution as “unacceptable”, while attacks from wild animals as “low”.

Table 4

Classification and Hazard Rating Number of identified risks.

* possible (2) = possible - but it is not common to occur (2).

All of the risks classified in Table 4 as high (falling objects and falls from height) and unacceptable (electrocution) should be put as priority in applying risk control measures, as those risks pose serious risk for the safety and health of involved workers.

3.3. Risk control

Previous studies were consulted in order to give suggestion on control measures for classified risks. Some measures control all of the classified risks, while some measures are specific for each risk.

In Table 5 were suggested control measures for falling objects and falls from height. As it was noticed in one study conducted on injuries from falling objects (Grivna et al., 2015), peak time of injury was from 10 am to 1 pm. The study suggested this could be related to tiredness and sleepiness of workers which increased as the lunch time approximated. The time of increased number of injuries could also be correlated with heat stress, as this time also represent peak in air temperatures. These are all factors which could be taken in consideration when planning the working activities. The same study found that falling objects most commonly affect/injure the extremities of the human body. The most affected were the upper extremities in 38.3%, followed by lower extremities in 37.6% and head/neck in 19.5%. This is important to consider, as it shows that hard hats (helmets) would only partially minimize the consequences of a falling object, and showing the importance of boots with protective cap and other PPE.

Table 5

Suggested control measures for falling objects and falls from height.

* Sources: Falling objects (Bastos et al., 2019; Grivna et al., 2015); Falls from height (Bastos et al., 2019; Zlatar et al., 2019).

Although falls could occur from different heights (including sitting or standing height), the falls from height (above 2 meters from the ground) are of particular interest for the occupational risk management. Falls from height can result in serious injuries or even death, even when the person didn’t fall directly on his head/neck. As concluded by one study (Zlatar et al., 2019), falls from height between 3 and 6.1m most commonly resulted in temporary disability (52% of analyzed cases), while in some cases even with permanent disability (15%) and death (25%). As the falling height increased, so did the severity of consequences, where falling from heights above 9.1m resulted in death in 73% of analyzed cases. As telecommunication antennas are normally put-on high altitudes (building roofs and towers), falls represent high risks which would normally result in death consequences.

When analyzing the cases of accidents of falls from height (Zlatar et al., 2019), it was noticed that in 98% of cases there were more failed risk control measures (missing or not adequately applied measures). This means that in the majority of cases, falls from height were not a coincidence or an unlucky event, but a result of various failed risk control measures. Non-adequate or non-existing procedures of work were present in 81.6% of analyzed accidents of falls from height, while engineering measures such as handrails, barriers and edge protection in 65.8% of cases. It is probable that analyzing accidents from other types of risks would lead to similar conclusions, indicating procedures of work as one of the main failed risk control measures.

In Table 6 were suggested control measures for electrocutions and attacks from wild animals. The risk of electrocutions was classified by the HRN as “unacceptable risk”, normally resulting from unsafe equipment or installation, unsafe environment and unsafe work practices (Occupational Safety and Health Administration, 2020). Electrocution is, along with falls and the impact of falling objects, one of the main causes for occupational fatal accidents (International Labour Organization, 2003).

Table 6

Suggested control measures for electrocutions and attacks from wild animals.

* Sources: Electrocution (Pereira et al., 2019; Zhao et al., 2015); Attacks from wild animals (Martins et al., 2018).

In order to contribute in the reduction of the number of accidents, OSHA developed a potential draft of the standard addressing telecommunications tower safety (Occupational Safety and Health Administration, 2018). The draft defined the minimum safety training for all employees working on telecommunications tower worksites, including trainings related to fall arrest system, environmental hazard recognition, electrical hazard recognition, first aid training, job hazard analysis. The perspective standard should also include topics such as assignment and roles training for authorized climber/rescuer, competent climber/rescuer, qualified rigger, hoist operator, crane operator, recordkeeping, worksite conditions (job hazard analysis, toolbox talks, rigging, hoisting, and gin pole use), environmental hazards (weather hazards, wildlife, worksite locations), safe work practices (general, structural work on telecommunications towers), considerations related to communication and structural alterations and/or modifications, fall protection (duty to have 100 percent fall protection; personal fall arrest systems; safety climb systems), support equipment requirements (hoisting, use of cranes in telecommunications tower work activities), structural requirements for telecommunication towers (structural loading considerations and tower inspection requirements), and the use of Unmanned Aerial Vehicles.

Further on, the occupational safety and health should be considered already at the initial phase, by applying the concept of prevention through design, which would provide a cheaper and a more effective risk control for towers and similar constructions. This could be achieved through Building Information Modeling (BIM) or similar platforms, which were already successfully used for different phases of the construction and maintenance process (Zlatar & Barkokébas Junior, 2018) for automatic, semi-automatic and manual identification and analysis of risks (Burgos da Rocha Leão et al., 2019). Such platforms were mostly used in managing risks of falls from height, falling objects and electrocutions. However, recent applications show BIM could be used even during the maintenance phase and for assessing exposure to noise levels (Tan et al., 2019) which show a range of perspectives for the application on telecommunication towers for assessing exposures to thermal environments or electromagnetic fields, or, adequately position the antenna to avoid excessive exposure of workers and the general public to radiofrequency fields .

The current study has several limitations. It is important to take in consideration that in additional to the mentioned risks of accidents, there are a number of health risks which should be additionally evaluated: ergonomic risks (musculoskeletal disorders); non-ionizing radiation (electromagnetic and solar); microclimate (thermal environment: hot or cold) among others. All these risks should be considered when assessing the risks to which the maintenance workers are exposed. This study was based only on data collected from nine workers and three companies. The present study had no access to buildings; therefore, it only considered maintenance of antennas on towers. Future studies could conduct additional studies on maintenance of antennas located on building roofs. Due to only few publications on the topic, more studies are needed regarding occupational safety and health in construction and maintenance of telecommunication towers.

5 Conclusions

The number of telecommunication towers is increasing worldwide, with expectations for them to continue to increase as the demand for service requires. This increase will mean that more workers will be participating in construction and maintenance activities of telecommunication towers.

These activities present high risks for occupational safety, namely related to falling objects (antennas and tools), falls from height, electrocutions, and attacks from wild animals. However, through the risk management process, as suggested through this study, it is possible to eliminate and/or minimize the risks. For this purpose, it is first important to apply different methods and techniques in order to identify, analyze and evaluate the risks, and then apply adequate control measures.

From the results of the current studies, it can be concluded that evaluated cases of maintenance activities in telecommunication towers have poor occupational safety conditions, with only 20% of considered items being in conformity, and 80% in non-conformity. This is in accordance with the findings from other encountered studies, which lead to accidents and fatal consequences.

The safety on telecommunication towers should be first improved through the concept of “Prevention Through Design”, where new technologies as the Building Information Modeling (BIM) and similar could be applied. For this purpose, the current study offered suggestions for risk control measures. In addition, it would be beneficial to consult the suggestions developed by OSHA trough the potential draft of the standard addressing telecommunications tower safety.

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Appendix A

Questionnaire applied to professionals who perform maintenance on antennas in telecommunications towers.

Appendix B

General company information.

Appendix C

Checklist das Normas Regulamentadoras and NBR 5419.

C = Compliance; NC = Non Compliance; NA = Not applicable.

Notes

Author notes

*tomi.zlatar@gmail.com