The breathing rate over the first 12 years of life is about double that of adult breathing rates. 
So our kids can take in double the amount of inhaled pollutants as an adult under the same situation of exposure.
When the breathing rate is taken into account relative to lung surface area, the amount of airborne contaminants reaching the lung surface is likely to be about 3-4 times higher in 3-month old children than in adults.
This makes children more vulnerable to the effects of spray drift and household insecticides. (काला Hit! : Oil Paints, Perfumes, Deodorants! ) On top of it, air pollution. On top of it, AC classrooms and bedrooms !
Side note: Is this the reason why we have निष्क्रमण संस्कार ? No exposure to outer world for first 4 months of life. So to avoid possible pollutants. On निष्क्रमण संस्कार day, introduce infant to mother nature and then later to other relatives. Till then, mother and child remain in controlled environment at new mother’s maternal home.
 Differences Between Children and Adults: Implications for Risk Assessment at California EPA
The California legislature enacted a law requiring the California Environmental Protection Agency (Cal/EPA) Office of Environmental Health Hazard Assessment (OEHHA) to evaluate whether our risk assessment methodologies are adequately protective of infants and children. In addition both OEHHA and the California Air Resources Board must examine whether the Ambient Air Quality Standards set for criteria air pollutants and the health values developed for air toxics are adequately protective of infants and children. We have initiated a program to look at potential differences in response to toxicants between children and adults. We are evaluating this issue from the perspective of exposure differences as well as toxicokinetic and toxicodynamic differences between children and adults. Data on specific chemicals are rather limited. As a result, we will be pooling information to determine whether there are generic differences between children and adults that may be applicable to risk assessment in general or to risk assessment of specific classes of compounds. This paper discusses the rationale for approaching the issue of determining whether our risk assessment methods are adequate for infants and children and includes a discussion of some of the available information on both qualitative and quantitative differences in response to toxicants between children and adults or immature and mature laboratory animals. We provide examples of differences between children and adults in absorption, metabolism, and excretion of toxicants as well as qualitative differences in toxic response.