Mapping susceptibility to air pollution and its association with birth defects: a tool for public health intervention

Epidemiological studies evaluating the relation of environmental air pollution (AP) and birth defect (BD) are relevant to public health. Some limitations on these studies may derive from multiple factors contributing to the spatial variation of AP. This study aimed to integrate multifactorial AP indicators into an index and explore its application in a case-control study conducted in Portugal between 2016 and 2021. Spatial multicriteria analysis was employed to identify areas susceptible to AP. Variables included: (i) Euclidean distance to industrial units; (ii) kernel estimation of industrial units density; (iii) land occupation; (iv) Euclidean distance to main roads; and (v) areas conductive to radiation fog formation. Variables were classified into high, moderate, and low susceptibility. An AP susceptibility map was generated using the weighted linear combination method, with the analytic hierarchy process assigning weights to the variables. Georeferenced BD cases and controls were overlaid with environmental exposure variables and the AP index. Three AP susceptibility areas were identified: consolidated urban, peri-urban area, and a residential-industrial area. In areas of high susceptibility, 47 cases (29%) and 65 controls (31%) were observed; and in areas of low susceptibility 25 cases (15%) and 21 controls (10%) were observed. The development of the AP susceptibility map has been demonstrated to be a valuable tool for identifying patterns, generating hypotheses regarding the potential environmental exposure of NB to AP agents during pregnancy. When integrated into more complex analyses, these findings may contribute to assess the potential risk factors that play a major role in BD.