Environment and Hazard -5

The ‘Home Environment’ plays an important role in many issues affecting child health across the globe. Children in general may be vulnerable and become exposed to various other household hazards such as exposures to known harmful building materials, chemicals, radon, drinking water and well-water and nitrogen dioxide.

Poor housing conditions and poor ventilation together with household air pollution may also increase the risks of child hood diseases. Indoor exposure to environmental tobacco smoke (ETS) may also be hazardous and contribute to health consequences like asthma in those children that are affected.

Full exposure Pathway

Exposures to tobacco smoking may occur at any level along the entire stages of human development and these may include preconception (maternal and paternal smoking), pregnancy (maternal smoking and passive smoking), infancy (passive smoking), childhood (passive and active smoking) and young and adulthood (active and passive smoking). ¹

Home

The key internal exposure pathways and their possible routes for exposure to tobacco smoking that may lead to asthma include;

1. In utero exposure ² – mainly concerns the maternal exposure to environmental tobacco smoke(ETS) associated with pregnancy via active or passive smoking.

Route: Trans placental

Mothers who are pregnant and are either active smokers or passive smokers run a risk of their developing foetus being exposed to the chemical toxicants of tobacco smoke transmitted via the placenta.² The tobacco smoke constituents are initially inhaled through the respiratory airways to the smaller airways in the lungs (bronchioles) and then absorbed through the tiny gas-exchanging airway sacs (alveoli) and into the maternal blood circulation.

2. Indoor air exposure – particularly ‘second hand smoke’, where the children at household level are frequently getting exposed if their family members are smokers. Studies have showed that children are (the two reasons highlighted). ³

Route: Inhalation

1. Active smoking – refers to the active smokers who inhale the undiluted smoke directly into their lungs from the end of cigarette which is called mainstream smoke (MS). ⁴ Theconstituents ofmainstream smoke are believed to contain higher in doses of tobacco chemicals compared to passive smoking.

2. Second Hand Smoking or Passive smoking- refers to the non-active smokers who mostly inhale what is called second-hand smoke (SHS) which is a mixture of side-stream smoke(SS) comprised of both the smoke from the glowing cigarette and the exhaled air (mainstream smoke)^.4 Thus, the side-stream smoke is diluted because it contains both the exhaled mainstream smoke and air and may be less in concentration of the tobacco chemical constituents.⁴

3. Third-hand smoke – refers to the surface-deposited tobacco smoke chemical components which may be left in indoor environments for periods that allow change to their compositions and render them harmful to humans especially infants and toddlers who commonly practice hand-mouth on contaminated surfaces^.5

Asthma

Asthma can be defined as an inflammatory airway disease involving inflammation and impairment of airway due to a complex interaction of immune cells and nonimmune environmental factors that trigger asthma such as tobacco smoking and second hand smoke. ⁶

Scope and nature of problem

Asthma is a very common chronic disease affecting children and is believed to affect almost 300 million people world-wide.⁷Evidence has shown that the prevalence of asthma has been on the rise in the last 50 years (Ref) with increasing trends noted in the industrialised and developed regions. The increase in the global burden of asthma disease ensures that important environmental factors that contribute to asthma are clearly identified for improved intervention and prevention strategies.

Risk factors

The risk factors for asthma that are commonly known include allergies, positive family history of asthma, cock-roach allergen, environmental tobacco smoke exposure(ETS), and prenatal smoking. ⁸ The diagram shown below in figure 1 summarises the early life risk factors for persistent asthma ⁹. It shows the different pathways in which environmental exposures and genetic predispositions lead to asthma. As illustrated, environmental exposures to tobacco smoke may affect a foetus in prenatal and later postnatal through impairment and inflammation of the lung resulting in asthma.