Children�s unique vulnerability
Children may be more vulnerable to the to the effect of air pollution than adults.Childen�s lungs growth and development is not complete at birth. Lungs growth and development is rapid and proceeds through proliferation of pulmonary alveoli and capillaries until the age of 2years.After birth,active formation of new alveoli occurs in the newborn with about 100,000,000 alveoli present for the first 2 years of life.Athough new alveoli can still be formed after the age of 2years with most of the growth occuring through an increase in the volume of existing alveoli.Thereafter,the lungs grow through alveolar expansion until 5-8years of age with about 300,000,000 alveoli present at 8years of age.Lungs do not complete their growth until full adult statures is achieved in adolescence(World Health Organization,2009).
Infants and young children have a higher resting metabolic rate and rate of oxygen consumption per unit body weight than adults because they have a larger surface per unit body weight and because they are growing rapidly. Because of this, their oxygen demand is higher and their respiratory rates is higher per unit body weight than adults. Therefore, their exposure to any air pollutant may be greater.(World Health Organization,2009). According to Sembulingam, (2012) ,normal ranges of respiratory rates in different ages are:
� Newborn:30 � 60cycles/minute
� Early childhood :20 -40cycles/minute
� Late childhood:15 � 25cycles/minute
� Adult:12-16 cycles/minute(Sembuligam et al,2012)
In addition to an increased need for oxygen relative to their size, children have narrower airways than those of adults. Thus, irritation caused by air pollution that would produce only a slight response in an adult can result in potentially significant obstruction in the airways of a young child.(World Health Oganization,2009).
Most newborns are obligate nose breathers.Coarse nose hairs filter out large particulate matter;the remaining nasal airways filter out particles as small as 6 microns in diameter.Particles greater than 10microns rarely make it past the upper airway,whereas fine particles smaller than 2microns can make it as far as the alveoli(World Health Orgaization,2009).
Respiratory particles and gasses affect different parts of the respiratory tract depending upon their inherent characteristics.For gases ,relative solubility is important.For particle,size is important. Compounds such as sulphur dioxide ,aldehydes,ammonia and chlorine because they are highly water soluble,initially affects the upper repiratory tract; ozone which has a medium water solubility initially affects the upper part of the lower respiratory tract and nitrogen dioxide and phosgene which has a low water solubility,initially affects the lower respiratory tract(World Health Organization,2009).
The effect of oedema on the adult airway is much less dramatic than it is on the newborn�s airway One millimeter of oedema reduces the diameter of the adult airway by about 19% whereas it reduces the diameter of the infant airway by 56%.Compared to adults the peripheral airway (bronchioles) is both relatively and absolutely smaller in infancy allowing intraluminal debris to cause proportionately greater obstruction(World Health Organization,2009).
In addition, infants have relatively greater mucous glands, with concomitant increase in
secretions. They also have potential for increased oedema because their airway mucosa is less tightly adherent. Lastly, there are fewer interalveolar pores (Kohn�s pores) in the infant, producing a negative effect on collateral ventilation and increasing the likelihood of
hyperinflation or atelectasis(World Health Organization,2009).
The resting minute ventilation normalized for body weight is more than double in a newborn infant (400 cc/min/kg) compared with an adult (150 cc/min/kg)(World Health Organization,2009).
MORTALITY
Acute respiratory infections are the major cause of mortality among children aged less than 5years especially in developing countries .Worldwide ,20% mortality among children aged less than five years is attributed to respiratory tract infections(predominantly pneumonia associated). If we include the neonatal pneumonia also in the pool,the burden comes around to be 35% to 40%among children aged less than 5years accounting for 2.04million deaths/year.Southeast Asia stands first in number for acute respiratory incidence,accounting for more than 80% of all incidences together with sub-Saharan African countries..In India more than 4lakh deaths every year are due to pneumonia accounting for 13% to 16% of all deaths in the paediatric hospital admissions(Vashistha,2010).Million deaths study based on the register general of India mortality statistics on the causes of neonatal and child mortality in India,(2010) had reported 369,000deaths due to pneumonia among children 1 to 59 months at tthe rate of 13.5/1000 life births .More number of deaths due to pneumonia was reported from central India.(Causes of neonatal and child mortality in india,2010).
MORBIDITY
Estimating the morbidity burden has inherent challenges due to lack of uniformity in study definitions,spectral nature of illness and misclassification errors.Recent estimates suggest 3.5% of the global burden of disease is caused by acute respiratory infections(Selvaraj et al,2014) .In developing countries on an average every child has five episodes of acute respiratory infections/year accounting for 30% to 50% of the total paediatric outpatient visits and 20% to 30% of the paediatric admissions(Selvaraj et al,2014) . Recent community-based estimates from prospective study report 70% of the childhood morbidities among children aged less than five years are due to acute respiratory infections(Dongre et al,2010).While in developing country,a child is likely to have around 0.3episodes of pneumonia/year,in developed countries it is 0.03 episodes per child/year . On this basis ,India is predicted to have over 700million episodes of acute respiratory infections and over 52million episodes of pneumonia every year.A study from Haryana by Broor et al(2007),had reported 2387,536, and 43 episodes of acute upper respiratory infections,acute lower respiratory infections,and severe lower respiratory infections,and severe acute lower respiratory infections respectively per 1000 child years.(Selvaraj et al,2014).
This is dummy text. It is not meant to be read. Accordingly, it is difficult to figure out when to end it. But then, this is dummy text. It is not meant to be read. Period.
ConversionConversion EmoticonEmoticon