What should one do if they are afflicted by cat urine, which is abundant in the slum area where they live?

The fundamental principle concerning things is purity. So, if you doubt the impurity of water that has touched you, consider it pure. This is the view held by Sheikh Ibn 'Uthaymeen. Based on this, the water that touches your face is deemed pure, and you are not required to wash it or change your clothes, unless you are certain that it is cat urine. In that case, only the impure spot must be washed, because cat urine is impure. We advise you to ignore obsessive thoughts and not pay attention to them.