Based on the three survey, in Ethiopia, more than 96% of the households use solid biomass fuel for cooking even if these fuels are known to be emitting large amount of indoor air pollutants which implies that the children’s exposure to biomass and charcoal fuel lead to high chance of getting ARI [27]. The finding also shows that 9.6% of the total households prepare food out-door which is different from the study conducted in African countries that reported 18% in East Africa and 43% in West Africa [28]. The difference could be due to variation in the types of cooking stoves used; having fixed or movable stove.
The average prevalence of ARI among children of under-five years old in three surveys (2005 to 2016) is 11.9% which is incomparable with the finding in the slum urban of Addis Ababa which is 23%[18] that could be because of a small number of samples considered in latter study. On the other hand, the finding is almost comparable with the finding from Tanzania, 11% [29], and East Africa, 10% [28].
The finding shows the association of place of cooking food with the prevalence of ARI in children in current study. In view of that, children whose mother prepare food outdoor are less likely to suffer from ARI by 68%, (AOR = 0.32, 95% CI = 0.10, 0.98). The current finding is consistent with a finding from 27 African countries that shows cooking out-doors is associated with a decrease in ARI by 0.5 percentage points compared to cooking indoors [28]. Moreover, a study conducted in Tanzania measured higher concentration of PM10 and NO2, which are predisposing factors for ARI, in the poorly ventilated indoor kitchens in the living room, compared to other locations that indicates cooking outdoor is safer than cooking indoor [29].
The current study shows cooking in separate building was not significantly different from with cooking inside building that could be due to mothers’ carrying their children to the building where they cook food, and the condition of the building like air ventilation, number of available windows, and window sizes which were not measured in the DHS survey. In this regard, studies conducted in one part of the country show that households in a ventilated kitchen had less to suffer from the disease compared to kitchen with no window and poorly ventilated houses [27].
The multilevel modeling shows that the odds of children to develop ARI is significantly different between children of within survey than children of different surveys which suggest that there is no progress in changing the practice of households either to use non-solid biomass or preparing their food outside and/or ventilated kitchen so that the risk will be minimized. On the other hand, there is great effort at the country level to improve the use of non-solid biomass like biogas and others [30–34].
The parents’ occupation, education status and wealth quintiles had no a statistical association with children’s ARI status though there is a prior study that shows socio-demographic characteristics mainly education and occupation had association with children ARI [7]. The mother’s watching of television at least once in a week is protective of her child to develop ARI while listening of radio is not. Exposure to mass media increases awareness and dissemination of knowledge about the programs and policies related to under-five children health care services as indicated in prior finding [35]. The discrepancy about radio might be because of the type of information disseminated and it’s persuasiveness that would lead to behavioral changes.
Regarding child related risk factors associated with ARI, risk of having ARI is 26%, 34% and 51% less likely respectively among children of aged 2–3 years, 3–4 years and 4–5 years compared to children of below one year which suggests the exposure of children for cooking induced indoor air pollutants decreases with age. The finding complies with a prior study in urban areas of Oromia region, Ethiopia [36]; in Wondo-Genet district, southern Ethiopia [19] and in Afghanistan [37]. This could be because of the few time the older children spend with their mothers in the house [37], and the higher number in younger children could be associated with the underdeveloped epithelial linings of the lungs and weaker immune system of younger children compared with the older counterparts [37–39].
The finding that the normal children’s risk of developing ARI is less likely compared to underweighted children that corroborate with the finding from India [40] and [41] is due to the fact that severely malnourished children are often immune-compressed and more prone for various infections. In addition, the under-weighted children’s respiratory tract mucosa also lacks an adequate protective ability against pathogenic microbes that commonly cause ARI India [40].