Second Hand Smoke and Preggo: SO and I have different opinions

Ok, I'm frustrated. This is my first pregnancy and I'm trying to ensure I do everything right. I asked my boyfriend to refrain from smoking around me; he says I'm overreacting. He said second hand smoke within a ventilated area (ex. a car with windows open) won't cause a problem. He says fears about smoke and pregnancy are all hysteria. I think he's crazy. Windows down or not (keeping with the example) I still inhale the smoke. And now I'm mad at him that he thinks I'm overreacting because I don't want smoke around me. I just want to protect our baby.