Studies have suggested that blood levels of benzene in children who play outdoors in inner city areas are nearly as high as those found in workers occupationally exposed in the petrochemical industry.3

Respiratory Development

Respiratory ailments are among the most common symptoms that cause parents to bring children to their doctor. Children are particularly vulnerable to respiratory conditions for a number of reasons involving features of their developmental stage, physical differences from adults and aspects of their behaviour.

Developmentally, a child’s respiratory anatomy is immature. The infant’s lungs are not fully developed at birth. Although bronchiolar branching is complete early in fetal life, alveolar development and cellular differentiation of lung tissue continues into adolescence. There is about a 23-fold increase in lung volume from birth (150-200 ml) to adulthood (5,000 ml) translating into a comparable increase in absorptive surface area.1

There are also physical reasons that children are more vulnerable. Smaller lungs mean a relatively higher surface area to volume ratio, such that children are already absorbing a greater volume of contaminants relative to their body size compared to adults.

Also, a child’s breathing rate is faster than that of an adult, so every minute they exchange more air per kilogram of body weight. Older children in particular display the maximum air intake because of their greater activity levels.

Being smaller in size, a child’s breathing zone is much lower than that of an adult. Some heavier contaminants, such as pesticides or automobile exhausts, are typically present in a vertical gradient, being in higher concentration closer to the ground, therefore closer to the child’s breathing zone.