AMBIENT AIR POLLUTION AND PREGNANCY OUTCOMES: A REVIEW OF THE LITERATURE

CHAPTER ONE

INTRODUCTION

1.1 Background to the study

There is extensive evidence that ambient air pollution affects human health (e.g., Brunekreef and Holgate 2002; Künzli et al. 2000; Pope et al. 2002). Most studies have focused on the effects of air pollution on adult mortality and respiratory morbidity (Dockery et al. 1993; Schwartz and Marcus 1990). However, some age groups appear to be more susceptible than others. For example, it has been shown that the effects are larger in the elderly than in the general adult population (Saldiva et al. 1995). Studies on childhood health risks, such as respiratory symptoms or hospital admissions for asthma, suggest that the opposite end of the age spectrum is also more vulnerable to air pollution than is the general population (Dockery and Pope 1994; Heinrich et al. 1999; Schwartz et al. 1994). In addition to these “traditional” end points in children, there is now emerging evidence that air pollution is also associated with ele- vated risk of adverse pregnancy outcomes (Glinianaia et al. 2004; Maisonet et al. 2004).

The study of birth outcomes is an impor- tant emerging field of environmental epidemiology. Birth outcomes are important in their own right because they are important indicators of the health of the newborns and infants. In addition, low birth weight (LBW), intrauterine growth retardation (IUGR), and impaired growth in the first years of life are known to influence the subsequent health status of individuals, including increased mortality and morbidity in childhood and an elevated risk of hypertension, coronary heart disease, and non-insulin-dependent diabetes in adulthood (Barker 1995; Osmond and Baker 2000).

It is increasingly apparent that there is a critical period of development when the tim- ing of exposure and the dose absorption rate can be even more important for the biologic effects than is the overall dose (Axelrod et al. 2001). Fetuses, in particular, are considered to be highly susceptible to a variety of toxicants because of their exposure pattern and physio- logic immaturity (Perera et al. 1999; Sˇrám 1999). Their developing organ systems can be more vulnerable to environmental toxicants during critical windows (sensitive periods of development) because of higher rates of cell proliferation or changing metabolic capabili- ties (Calabrese 1986). Therefore, prenatal exposure to environmental pollution can result in some adverse reproductive outcomes, similar to the association between maternal active and passive smoking and impaired reproductive outcomes (Misra and Nguyen 1999; Salihu et al. 2004). The specific mechanisms that may account for the link between ambient air pollution and adverse reproductive outcomes are also reviewed in this study.

The objective of this review is to examine the evidence linking adverse birth outcomes with ambient air pollution. For the purpose of this review, birth outcomes have been divided into five groups: a) mortality of fetuses and infants, b) LBW, c) premature (preterm) births, d) IUGR, and e) birth defects. In this article we review the evidence on each of these separately. For each of the outcomes, we assess the three critical issues in interpreting epidemiologic studies (random error, selection or measurement bias, and confounding); issues related to all reviewed outcomes (e.g., publication bias or biologic plausibility) are considered together at the end of the article. By weighting the evidence, we attempt to draw balanced conclusions about the relations between air pollution and birth outcomes

1.2 Statement Of The Problem

Health, it is said is wealth, and without it the earth remain empty. Our environment must be friendly if we must have good health. Good health although promoted by nutrition, physical exercises etc, can hardly be attainable if, environmental problems like air pollution is not addressed. The environmental degradation occasioned by fumes from industrial, commercial, domestic and transportation activities affect health tremendously. For instance, carbon iv oxide is known to have negative effect on ozone layer and consequently cause severe heat to human being.

However, air pollution following human activities in Uyo constitutes a source of ailment to humanity. This is because carbon monoxide when released to air or inhaled can combine readily with hemoglobin and posed a threat to human health. Sometimes, in high concentrations, it (carbon monoxide) causes dizziness, headache, nausea, tiredness, and even brain damage when inhaled for a long period. lnfact, the alarming rate of health problems and issues in the society are to a large extent traceable to environmental health hazard mostly air pollution.

Moreover, preliminary diseases like lose of vision, abdominal pain itching and even cancer are caused by fuel gases. Therefore, it is as a result of the above mentioned problems, that this study is critically investigates the implication of continued ambient air pollution on pregnancy outcome.

Objective of the study

The main objective of the study is to examine the effect of ambient air pollution and pregnancy outcomes. Specifically, the study aims to

1. examine the effect of Air pollution on child mortality

2. examine the effect of Air pollution on birth weight

3. examine the effect of Air pollution on premature births

4. examine the relationship between Air pollution and birth defects

Significance of the study

The study is crucial to the environmental degradation control, particularly air pollution. The researcher would make sure that the outcome emanating from the study go along way to helping solve environmental health problem in Nigeria.

Beside, students from urban and Regional Planning and other related discipline would see the work invaluable for further study. Again, the researcher would ensure that findings from the study broaden the scope of the field (Urban and Regional Planning).

1.5 Research question

 1. what is the effect of Air pollution on child mortality ?

2. what is the effect of Air pollution on birth weight ?

3. what is the effect of Air pollution on premature births ?

4. what is the relationship between Air pollution and birth defects ?

1.6    Scope Of The Study

Uyo is a capital of geographical entity called Akwa Ibom State. Because of its status, it has attracted attention from all sections of the state and swelled the city with various economic activities. Here we have services, commercial, industrial and transportation activities. These activities however, cause pollution.

As witnessed daily, services, transportation, religious and domestic activities promote air pollution because of intensive use of electrical sets. The fumes emanated from the usage of the electrical generating plant contained poisonous gases which are dangerous to health. Therefore, it is as a result of negative effects of fumes to the health of Uyo residence that this research investigates the pregnancy outcomes (implication) of the air pollution. The study would only be focused to health related problems associated with air pollution in Nigeria, with Uyo being the case study.