Occupational hazards of Brazilian solid waste workers : a systematic literature review

Background
In Brazil, urban cleaning professionals play an important role within a context characterized by annual increase of the garbage production. However, the job exposes such workers to various occupational hazards, an issue little discussed in the literature.


Objective
To identify occupational hazards to which Brazilian solid workers are exposed, as well as factors associated with their minimization.


Methods
A systematic review of the literature was performed in databases Scientific Electronic Library Online (SciELO), Latin American and Caribbean Literature in Health Sciences (LILACS), and PubMed. Gray literature was also searched through Google Scholar and included studies published along a ten-year period (2006-2016) in Portuguese, English, and Spanish.


Results
Twelve studies were located; the results showed that waste workers were exposed to biological, accidental, chemical, ergonomic, physical, and psychosocial risks. The risks declined with adherence to use of personal protective equipment and guidance for workers, employers, and population.


Conclusions
Given the few studies in this field, more evidence-based research is necessary to serve as grounds for the development and implementation of public health policies aiming at reducing occupational risks among the studied population.

Occupational hazards in Brazilian solid waste workers

INTRODUCTION
Each year, about 1.3 billion tons of solid waste are generated worldwide.By 2025, this volume is expected to reach up to 2.2 billion tons annually, which is a cause of concern for governments and society 1 .
Brazil is one of the nations that produces the largest amount of waste, following the increase of its population (currently 200.4 million) each year 2 .The country generates nearly 80 million tons of solid waste per year, being elected as the third largest waste producer in the planet 3 .The situation is more concerning due to the fact that professionals involved with waste collection in the country do not receive the attention deserved by municipal authorities or attributable respect from the society 4 .
In Brazil, the job of garbage professionals requires much effort to be accomplished, given the nature of the work, workplace conditions, besides predictable and unpredictable variables that follow their routine 5 .It is contended that those professionals are exposed to a variety of occupational hazards 6 , most of them not discussed within scientific literature in a context where such individuals face social stereotyping as an effect of cultural influences 7 .
Thus, guided by the research question "What are the occupational hazards to which solid waste workers are exposed in Brazil?", a systematic review was conducted in order to identify occupational hazards that affect those professionals as well as factors associated with hazard minimization in this group.

STUDY DESIGN AND SEARCH STRATEGY
A systematic review of national and international literature was conducted which aimed to identify occupational hazards that affect Brazilian waste workers, as well as the factors that contribute to the minimization of hazards in the given population.
Data were collected from November to December of 2016 in two distinct, respective stages (S1 and S2).For S1, three authors performed an independent search on the electronic databases: Scientific Electronic Library Online (ScIELO), Latin American and Caribbean Literature in Health Sciences (LILACS), and PubMed.On the other end of the spectrum, for S2, the three researchers searched gray literature studies through Google Scholar, considering the small number of publications on the topic yielded from the electronic search.
For both stages and all databases, the following search strategy and terms were used:

ELIGIBILITY CRITERIA
Complete studies published between 2006 and 2016 in English, Portuguese, or Spanish were considered for analysis as long as they had the primary purpose of examining occupational hazards in Brazilian waste workers.The authors did not include literature reviews or studies whose subjects were not legally employed waste professionals (i.e.homeless persons or individuals from non-governmental organizations collecting garbage for personal or community purposes).Studies on individuals involved in recycling were also not considered.

STUDY SELECTION AND DATA EXTRACTION
For the selection of studies, instructions provided by Moher et al. in Preferred Reporting Items for Systematic Reviews and Meta-Analyses: The PRISMA Statement 8 were followed.Once eligible literature was identified, they were exported to Mendeley, a reference manager, in order to organize titles by author and year of publication, excluding duplicates.
Eligible studies were read in full text and relevant data were extracted.Reference lists were also assessed.Finally, quantitative and qualitative data were segregated into categories for analysis.Microsoft Office Excel was utilized for further graphic representation.

REVIEW OF PAPERS
For this systematic review, the electronic and gray literature search yielded a total of 76 documents, which gave us an initial idea of the small number of publications on the topic.Only 57 studies remained after exclusion of duplicates.Then, the literature was screened for relevance after reading their titles and abstracts, and 18 publications remained.However, not all of the remaining publications met the inclusion criteria, leaving the final number of studies to 12, which then had their reference lists screened with no more studies included (Figure 1).

STUDY CHARACTERISTICS
The few studies identified in the database search and in the gray literature are presented in chronological order and include information about author/year of publication, method, objective, and results.The selected papers were mostly cross-sectional studies (92%), with a quantitative approach (Chart 1).
In a chronological analysis, one study dealing with occupational hazards in urban waste collectors 9 was identified for the year of 2006.However, no studies on the topic published in 2007 were identified.In 2008, there was one publication 14 and for each of the two subsequent years there were two publications 10,[15][16][17] .It was possible to identify a single publication on the subject being published in 2011 11 and two in the following year 18,19 .In 2013, 2014, and 2015, there were no published studies on the topic.Nevertheless, for 2016, three studies were encountered 12,13,20 .The fact points out a constancy in the number of published studies on occupational hazards in garbage workers.
All of the selected publications sought to identify the occupational hazards to which waste workers are exposed in several Brazilian cities.Others also discussed a variety of diseases resulting from that career, while a few of them also addressed how to minimize or prevent occupational hazards.With that being said, the thematic analysis was based on the following themes: types of occupational hazards in urban waste workers and hazard prevention measures.

OCCUPATIONAL HAZARD IN WASTE WORKERS
In developing countries, waste management procedures are characterized by a dominance of manual labor tasks, which therefore exposes waste professionals to a number of  occupational hazards of variable nature, occurring at every stage of the waste management process 21,22 .
Considering the possible occupational hazards in the workplace, the Brazilian Ministry of Labor designed a standardized set of colors to indicate the main potential risks to which workers are exposed in the various worksites.The colors are as follows: green is used to represent physical hazards, red for chemicals, brown for any biological hazard, yellow for ergonomic (or "human" factors), and blue to represent hazards related to accidents 23 .The psychosocial hazard, which was also evidenced in the literature 18 , used to be associated with the ergonomic hazard; however, it has been considered a new category 24 , without a standardized color representation, therefore why the authors attributed to it the gray color.
From the analysis of the publications, it was observed that waste management workers are exposed to five main occupational hazards, besides psychosocial hazards.Figure 2 shows the percentage of occupational hazards in those workers based on how much evidence was encountered, considering the number of times that hazards were cited in eligible studies.
Thus, the most evidenced hazards experienced by garbage workers were those of biological nature and accidents, respectively.The most common events happening to those professionals in the workplace are presented in Chart 2.

BIOLOGICAL HAZARD
Biological hazard is the likelihood of exposure to microorganisms with potential to cause harm to the worker's health.Throughout the studies, it was identified that waste workers are exposed to contamination by viruses, bacteria 10,14,[16][17][18] , fungi 14,19 , and parasites 9,12 ; all which can lead to acute or chronic infections, allergic reactions, and toxic reactions 23,25 .
Garbage management workers are susceptible to several biological damages that lead to the acquisition of several infections [16][17][18] .Sousa et al. (2015), attribute these infections not only to contact with waste, but to sewage and gallery contaminants that contain improperly discarded waste 26 .Contamination with the hepatitis C virus and tetanus bacteria were also mentioned with gastroenteritis appearing more evident in those workers, therefore culminating an increase in diarrheal conditions 12,18 .
In a study carried out in 2006, with a sample of 22 solid waste workers, it was identified the prevalence of 63.66% for parasites or commensals in those individuals, after a laboratorial analysis of feces.Of this percentage, 78.6% corresponded to protozoa while 21.4% to helminths (Entamoeba coli, Entamoeba hartmanni, Entamoeba histolytica, Endolimax nana, Ascaris lumbricoides, Trichuris trichiura, Strongyloides stercoralis) 9 .For these studies, it Occupational hazards in Brazilian solid waste workers Chart 2. Classification of the main occupational hazards to which waste workers are exposed according to their nature as evidenced in the literature.

Physical hazard Chemical hazard Biological hazard Ergonomic hazard Accident hazard Psychosocial hazard
Excessive noise, vibration, odor, solar radiation, and rainfall 14,18 .
Devaluation at work, lack of training, and disrespect of society 18 .
is important to note the difference between such species.Helminths constitute any disease-causing organisms that live on a human or another animal and derive nourishment from their host 27 , whereas a protozoa is defined as any parasitic single-celled organism that can divide only within a host organism 28 .
Another study also performed similar analysis in 185 workers, identifying the presence of protozoan infection, with sweepers being the most affected (55.9%).In addition, the author identified the incidence of sinusitis in the last twelve months (between 14.7% and 37.8%) and pneumonia (between 8.8% and 22.2%), with waste truck drivers being the most affected.In the evaluation of the positivity for hepatitis B and leptospirosis, it was identified that the sweepers are the most affected (incidence between 20% and 25.7%, respectively) 10 .
In a recent study, Santos (2016) identified the prevalence of soil transmitted helminthiasis above 35% in a sample of 163 workers in Piauí state, northeastern Brazil.The results were obtained from parasitological tests, with a prevalence of 25.15% for ascariasis, 7.36% for trichuriasis, and 9.82% for hookworm 12 .
Another important aggravation reported in the literature was dermatitis, which can be from fungal origin as well as an immune reaction against antigens.Dermatitis was the complaint of 6% of the 16 individuals assessed in a study of 2008 14 .Yet, in a study with a larger sample of 97 individuals, Coelho (2012) identified a higher prevalence of dermatitis in waste workers (42%), occurring more commonly on the hands 19 .Other diseases often found in those professionals are brucellosis, dengue fever, yellow fever, rabies, viral hepatitis (A, B, C, D, and E), leishmaniosis, and cysticercosis 29 .
Yet, in the context of biological hazards, although not mentioned in the studies found, prions also constitute infectious agents of relevance in waste management.Those protein-composed agents are found to be the cause of occupational diseases in some studies 30 .

ACCIDENT HAZARD
The risk of accidents -understood as any probability of exposure to a factor that places the worker in a vulnerable situation, affecting their physical integrity and well-beingseems to be a cause of great concern in such professionals 23 .An accident is defined as a sudden and unexpected event that can cause damage not only to the worker, but also to the property or work environment 31 .
In solid waste workers, accident hazards originate from a variety of causes.The literature points out that those workers are exposed to injuries from sharp objects such as glasses, syringes, nails, spikes, and thorns 11,14 .Some authors 15,18,20 also evidence the risk of slips and falls.
Authors also concluded that waste collectors are exposed to the risk of being run over, which according to Pedrosa (2010) is mentioned by 16% of the 96 individuals interviewed in in his survey 16 .Other hazards include animal attacks, especially dog attack 15 , press, and amputations through equipment used at work 20 .

CHEMICAL, ERGONOMIC, AND PSYCHOSOCIAL HAZARDS
Professionals involved in waste management are also susceptible to chemical hazards, when there is a likelihood of contact with chemical agents, including substances, compounds, or products capable of penetrating the body through the respiratory tract, skin contact, or ingestion 32 .In this regard, workers are exposed to manure, smoke, and other toxic substances that are erroneously discarded in the trash, such as pesticides, oils, and batteries 11,20,26 .
Ergonomic hazard is another occupational health risk affecting solid waste workers, which consists in the probability of a treat to the musculoskeletal system due to different factors, such as inadequate posture, excessive weight, excessive or repetitive physical exertion, among others 23,33 .The literature has shown that those individuals have suffered from postural, spinal, and muscle strain problems as a result of the weight they have to carry, as well as the repetitiveness and effort required to perform the functions at work throughout a long shift 13,18 .
In relation to the physical hazard, being the possibility of damage due to exposure to the different forms of energy, it was verified that waste management professionals suffer strong exposure to solar radiation, with intense heat or cold alongside exposure to climatic changes.In addition, they are subject to noise and intense vibrations caused by work equipment, therefore leading to hearing loss 14,18,26 .
Finally, one of the least explored hazards in occupational health 24 , psychosocial hazard has been evidenced in recently published literature 26 .From the literature analyzed, the authors were able to identify that waste workers continue to suffer from a historical discrimination, with the devaluation of their work by society, government, and employees, along with precarious working conditions, and an overall lack of training 18,26 .

PREVENTION OF OCCUPATIONAL HAZARDS IN SOLID WASTE WORKERS
In a context where there are several occupational hazards affecting solid waste professionals with different etiologies, the use of Personal Protective Equipment (PPE) has been the most effective in contributing to the minimization or elimination of exposure.However, it is a fact of negligence on the part of workers or even employers towards the use and mandatory compliance of PPE, respectively 15,17,18 .In addition, it is of the utmost importance that there be ongoing guidance programs for workers on the correct use of PPE and handling of urban waste 20 .
Orientation to the population towards the proper disposal of domestic waste seems to be another factor contributing to minimization of occupational hazards in garbage workers 11 .In this way, by combining these actions, the occupational risks can be reduced 26 .

LIMITATIONS OF THE STUDY
This study has some limitations derived from the fact that there are few national or international publications on occupational hazards affecting Brazilian solid waste workers available on electronic databases.For this reason, the authors included gray literature studies (undergraduate or master's degree paper), none of which negatively affect the quality of this review, based on validation by at least two individuals holding a Master's degree.
Another limitation refers to the generality of the results, which may be compromised since they represent only Brazilian data and are certainly consequences of policy and culture specific to the country.Nevertheless, considering the fact that most developing countries use the same procedures for waste management, mostly involving manual labor, the conclusions obtained through this study can be similar to the ones from future studies conducted in other developing countries.

CONCLUSION
From the analysis of the literature, it was possible to identify that solid waste workers are exposed to the five main occupational hazards.According to theis nature, they are classified as follows: biological, accidental, chemical, ergonomical, and psychosocial hazards.In order to contribute to the minimization and/or elimination of many of these risks, it is necessary to identify the importance of the combination of the guided use of PPE, training to the worker, and orientation to the population on the proper disposal of trash.
There are still few studies on occupational hazard in solid waste workers, which probably reflects the historical and social stereotyping faced by those professionals.Thus, the authors should emphasize the need for more evidence-based research that could serve as a subsidy for the development and implementation of public policies that are favorable to the reduction of occupational risks in the group studied.

Figure 1 .
Figure 1.Flowchart for the review of papers.

Figure 2 .
Figure 2. Literature evidence for studies on occupational hazards in waste workers.
Results from electronic database and gray literature search displayed in chronological order.
falls, and constant exposure to biological agents.Contributing factors to increase accidents: non-compliance with safety norms and procedures, lack of attention, and absence of PPE.Chart 1.