First thought is location due to roads. Particulate matter might be a factor, as well as diet. Dietary quality equality is not something I hear getting mentioned but could be a large component of any plan to seriously address disparities like this. We know that working classes tend to have worse diets, a stress related response but also has an affordability component since agricultural subsidies tend to favour the end product of unhealthy foods, which are then cheaper..

I assume hispanics might be more rurally located (pure assumption here). Another factor could be connections between autoimmune disease, MS and vitamin D.