Hi my friend,
Well let me ask you a question, as I think it will lead to the answer to the question you are asking about. Do you wash your hand after handling mangoes? Well of course you don't, and if you do, it is probably because you wash your hands after eating any fruit, right? Well do you know that mango skin / mango trees contain a similar oil to that produced in poison ivy, thus handling mangoes can cause a rash? Yet many people handle this damned fruit without a care in the world.
That is how I feel about bootleg carts. We need to remember that these games were manufactured for kids. Maybe some companies used lead to make their products, who knows, but if you look at folks from South America, Africa, Asia, and Eastern Europe - they aren't dying or getting ill just because they handled a few bootleg videogames sometime in the past, without washing their hands. Likewise, you probably won't either, so this is something I honestly wouldn't worry about at all.