Air pollution, migrants’ health inequality, and China’s Cross-regional Medical Insurance Scheme: a moderating effect analysis

Health inequality induced by environmental degradation has become a growing global concern. Especially for migrants across different medical insurance pooling regions, the problem is even more serious. Drawing on micro-level data from the China Health and Retirement Longitudinal Survey (CHARLS) and official air pollution data, we employ a two-stage least squares (2SLS) estimation strategy that adopts a relative deprivation perspective to identify causal effects. The findings suggest that air pollution significantly worsens health inequality, particularly among women, the elderly, and socioeconomically disadvantaged groups. Furthermore, the analysis reveals that Cross-regional Medical Insurance Scheme(CRMIS) plays a mitigating role in reducing inequality caused by air pollution. For migrants, choosing the medical insurance in the inflow region can alleviate the severity of health inequalities caused by air pollution. This research contributes to the global literature on environmental inequality by highlighting how institutional mechanisms, such as portable health insurance, can buffer the unequal health impacts of pollution. The insights derived from China’s experience offer valuable policy implications for other countries facing rapid urbanization, internal migration, and rising environmental health risks.