This paper investigates causal relationships between socioeconomic variables and environmental degradation using Directed Acyclic Graphs (DAGs). Cross-sectional (country) data on sulfur dioxide (SO2) emission, GDP, international trade, and an index of democracy are mainly studied. Recently developed algorithms are applied to these data in order to identify their underlying contemporaneous causal structure. This structure is then imposed in estimating an environmental quality equation. The key empirical results are that higher democracy level and openness give positive causes of air quality. A country's democratic level is a dominant causal variable in affecting environmental quality. However, a causal flow from GDP to SO2 emission witch is famously known as environmental Kuznets curve (EKC) was not clearly found.