1.1 Background of the study
The health effects of air pollution exposure have become an area of increasing focus in the past 30 years. A growing body of evidence has demonstrated that there are serious health consequences to community air pollution and that these consequences are not spread equally among the population. The description of the impact of air pollutants on children's health is complicated by the fact that there are a number of types of air pollution and a variety of indicators of adverse health effects. In the discussion that follows, the classification is by observed outcome; and the probable pollutants responsible are noted in each section. Over the past 5 years, investigators have been increasingly interested in studying the impact of air pollutants on children. There are several reasons for this, of which the lack of interference from cigarette smoking is one, and the increasing evidence that adult chronic respiratory disease may have its roots in childhood is another. Children have been shown to be at particular risk for other effects of air pollution, as detailed below. This research cannot be a comprehensive review of the literature, because recent reviews of airborne particles and ozone alone have hundreds of pages summarizing the literature. Rather, this work will cover the major health effects in children that have been linked to air pollution, cite some key papers, and discuss the strength of the evidence and also highlight areas where it seems that differences between adults and children, particularly in the development of the respiratory and immune system, suggest different impacts of exposure for children.
Air pollution has become a major global threat to human health. Historically, multiple major episodes of air pollution occurred worldwide in the early twentieth century have produced severe health outcomes.A large number of studies conducted worldwide by different research groups have demonstrated excessive mortality [1-8] and morbidity [9-18] associated with increases in air pollution. Some have pointed out children as a group highly susceptible to the effects of air pollution, mainly in terms of respiratory diseases [6, 9, 12-14, 16-18].Despite the increasing number of studies in this area, there are still points that deserve further clarification. While air pollution has decreased in urban areas of developed countries, high air pollutant concentrations have been recorded in large urban conglomerates of the developing world [6, 7].Exposure to air pollutants mostly occurs in industrial and rural areas due to various manufacturing, travelling, and living activities. Multiple review articles and meta-analyses have described a direct impact of air pollutants on respiratory responses and diseases. [3, 4, 5, 6, 7]
Respiratory health disease such as Asthma, which is characterized by reversible airway obstruction and inflammation, is the most frequent chronic disease in children. Recent global studies showed, although the rising trends in occurrence of allergic diseases in children appear to have levelled off or even reversed in many developed countries, while in many developing countries, the increase in prevalence has only recently started [19, 20]. These findings indicate that the global burden of asthma is continuing to be rising with the global prevalence differences lessening . It has been suggested that this increase cannot be explained by genetic factors and improvements in diagnostic methods alone. Comparative studies of the population of the same ethnic background living in different environments revealed important environmental risk factors for asthma, especially for ambient air pollution, which may play an important role in the development of asthma symptoms  . A systematic review concluded that, although weather, pollen, and environmental tobacco smoke (ETS) are important risk factors for asthma, each has been found to act independently of air pollution, and thus they do not explain the association between air pollution and asthma .
Comparing with the adults, children appear to be most vulnerable to the harmful effects of air pollutants exposure due to their stage of physical growth, immature immune system, and development of lung function with increased permeability of the respiratory epithelium.  Children also inhale a higher volume of air per body weight compared with adults,  delivering higher doses of different compositions that may remain in the lung for a longer duration . Another source of increased sensitivity of children to air pollution may be the qualitative and quantitative differences in the respiratory, immune, endocrine, and nervous systems during stages of rapid growth and development . Although epidemiologic studies have shown associations between asthma outcomes and routinely monitored air pollutants including particulate matter (PM), sulfur dioxide (SO2), nitrogen oxides (NO2) and ozone (O3), the contribution of ambient air pollution exposure to children’s asthma seems to varying different parts of the world, perhaps because of the difference in spatial and temporal variability of air pollutants sources and composition between different regions [28, 29, 30] and also, it still remains unclear whether the association of the pollutants with increased asthma prevalence in children is independent of each other or is attributable to other toxic air pollutants, such as combustion-related organic compounds that are not routinely monitored .
The human health effects due to air pollutants include carcinogenicity, pulmonary tuberculosis, cerebrospinal meningitis, pneumonia, whooping cough and measles [32-33] while the environmental effect is global warming. The health effects which are due to air pollution are called epidemiological diseases. These diseases are well-defined by [32-33]. The lung is not well formed at birth, and development of full functionality does not occur until approximately 6 years of age. During early childhood, the bronchial tree is still developing. For example, the number of alveoli in the human lung increases from 24 million at birth to 257 million at age 4,  and the lung epithelium is not fully developed. Children also have a larger lung surface area per kilogram of body weight than adults and, under normal breathing, breathe 50% more air per kilogram of body weight than adults. This process of early growth and development, the outcome of which is important for the future health of the child, suggests that there is a critical exposure time when air pollution may have lasting effects on respiratory health.
At the same time the child’s lung is developing, the child’s immune system, immature at birth, is also beginning to develop. Much recent attention in asthma research has been focused on this development, in particular factors that influence the development of TH-2 (humoral immunity dominant) versus TH-1 (cellular immunity dominant) phenotypes.  Another major factor that influences the relative effect of air pollution on children respiratory health is exposure. Children spend more time outdoors particularly in the summer and in the late afternoon.  Some of that time is spent in activities that increase ventilation rates. This can increase the exposure to air pollutants compared with adults, as indoor concentrations of air pollutants of outdoor origin are usually lower. Damage to the respiratory system in children can be devastating and permanent, and the adverse effects of air pollution may be obvious in adult life owing to long latent periods for several chronic diseases, including cancer. Therefore, there is need to carry out the research on effect of air pollution on children respiratory health in Port Harcourt.
1.2 Statement of Problem
Children represent the largest subgroup of the population susceptible to the adverse health effects of air pollution be it urban or rural.Air pollutants cause a wide range of acute and chronic effects in the respiratory system of children. Approximately 4 million deaths globally were attributed to respiratory infections between 2016 and 2017. Damage to the respiratory system in children can be devastating and permanent, and the adverse effects of air pollution may be obvious in adult life owing to long latent periods for several chronic diseases, including cancer.
Given this background, it seemed important to assess the respiratory health of children in Port Harcourt where the level of air pollution is still much above the National Ambient Air Quality Standards (NAAQS). Air pollution is viewed as a serious problem in Nigeria and Port Harcourt in particular. The Port Harcourt city has the dubious distinction of being one of the most polluted cities in the Nigeria. The major sources of air pollution in Port Harcourt are road traffic (72%), industrial emissions (20%), and emissions from household activities (8%). Soil re-suspension is also an important source of air pollution in the city . The above without doubt are likely to impede the health of children in the area.Accordingly, the study reported here was undertaken to examine the respiratory health of children in Port Harcourt.
1.3 Objective of the Study
The major aim of the study is to examine the effects of air pollution on children respiratory health. Other specific objectives of the study are;
1.4 Research Questions
H0:There is no significant effect on air pollution on children respiratory health in Port Harcourt
H1:There is a significant effect on air pollution on children respiratory health in Port Harcourt
H0: There is no significant relationship between air pollution and children respiratory tract infection in Port Harcourt
H1: There is a significant relationship between air pollution and children respiratory tract infection in Port Harcourt
1.6 Scope/limitation of Study
The study is restricted to the effect of air pollution on children respiratory health in Port Harcourt as the case study.
Financial constraint- Insufficient fund tends to impede the efficiency of the researcher in sourcing for the relevant materials, literature or information and in the process of data collection (internet, questionnaire and interview).
Time constraint- The researcher will simultaneously engage in this study with other academic work. This consequently will cut down on the time devoted for the research work.
1.8 Delimitation of Study
The study was delimited to:
- Health hazards that may be created by industrial operations.
- Port Harcourt metropolis of Rivers State
- Children and inhabitants of the industrial areas.
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