Background: Globally, observational studies have demonstrated an increase in emergency department attendances and hospital admissions in children with asthma exacerbations exposed to high levels of air pollution. Inconsistences in reporting severity of asthma attacks makes it challenging to establish the relationship between air pollution and near fatal and fatal asthma attacks. 

Objective: Systematic review to assess the association between ambient outdoor air pollution and fatal and/or near fatal asthma attacks. 

Methods: MEDLINE, EMBASE, Web of Science, Scopus and Open Grey electronic databases were searched for asthma attacks related to air pollutants (particulate matter (PM), sulphur dioxide, nitrogen dioxide, black carbon and ozone) in children aged 2 - 18 years. Identified studies were manually screened for fatal and near fatal attacks. Near fatal attacks were defined as requiring intensive care (ICU) management. 

Results: Two independent reviewers screened 1073 papers. 243 studies identified asthma attacks related to air pollution. 7 observational studies described fatal and near fatal events, of which 3 addressed near fatal asthma. PM2.5 and ozone (22ppb) were associated with near fatal attacks by one study (RR 1.26 CI (1.10-1.44)). Black carbon was not shown to have significant effect on ICU admission compared to no ICU admission (p=0.67). PM10 was observed to impact ICU admission in the context of thunderstorm asthma. Studies addressing mortality included children but did not demarcate age within analysis. 

Conclusions: Ozone and PM2.5 have been associated with near fatal and fatal asthma attacks in children. Synthesis of studies is limited by heterogeneity.