The sheer numbers of children affected (by indoor and outdoor pollution) are staggering. Based on satellite imagery, in the first analysis of its kind, this report shows that around the world today, 300 million children live in areas with extremely toxic levels of air pollution. Approximately 2 billion children live in areas where pollution levels exceed the minimum air quality standards set by the World Health Organization. These data don’t account for the millions of children exposed to air pollution inside the home.
The impact is commensurately shocking. Every year, nearly 600,000 children under the age of five die from diseases caused or exacerbated by the effects of indoor and outdoor air pollution. Millions more suffer from respiratory diseases that diminish their resilience and affect their physical and cognitive development.
Together, outdoor and indoor air pollution are directly linked with pneumonia and other respiratory diseases that account for almost one in 10 under-five deaths, making air pollution one of the leading dangers to children’s health.
From a 2016 report on the economic costs of certain health issues caused by exposure to indoor dampness and mold in the U.S.
This researcher estimated the costs of allergic rhinitis, acute bronchitis and asthma caused by exposure to indoor dampness and mold in the U.S.40 He used two methods—cost of illness (COI) and willingness to pay (WTP). 
WTP measures the full cost to society, but WTP estimates are difficult to compute and rarely available. COI methods are more often used but less likely to reflect full costs.
Based on the data available, he estimates the total annual costs as follows:
Allergic Rhinitis $3.7 billion
Acute Bronchitis $1.9 billion
Asthma Morbidity $15.1 billion
Asthma Mortality $1.7 billion