There is a difference between lead in paint and in fuel additives and the lead used in wheel weights. An ounce of lead used in a chemical compund is going to be much more pervasive in the environment than an ounce of lead in a solid wheel weight.
That solid chunk of lead, if it ends up in coastal waters at all, is going to be embedded in the bottom and that will pretty much take it out of circluation. Silt deposition has been doing that efficiently for billions of years with heavy metals, various carbon compounds, etc. What makes lead dangerous in the environment is when it is broken down to lead molecules or very small bits of lead for industrial use.
Banning lead wheel weights is just another one of those totally ineffective and meaningless "feel good" laws that end up costing everyone a lot of money and results in no significant benefit to anyone.