Breast-feeding and SUV-driving: what are the ethically relevant differences?

I’m not sure I realized it while I was writing it, but my last post (on whether scientific knowledge about the benefits of breast-feeding imposes any particular obligations) has me thinking about another kind of case where scientific knowledge might — or might not — bring ethical consequences.
That case? Global warming.
My big question, thinking about these two instances where scientific knowledge, individual decisions, and public policy all coalesce, is what the relevant differences are.

First, the disclaimer: I am not an expert in the scientific literature on the health effects of breast-deeding, nor am I a climate scientist. I’m going to make particular assumptions for the sake of argument. In the case that those assumptions fail, all bets are off.
So, for the sake of argument, let’s assume the following:

1. Breast-feeding has non-negligible positive effects on the health of the infants being breast-fed (compared to being fed infant formula instead of breast-milk).
2. Being fed breast-milk and formula confers fewer positive effects on health than being fed breast-milk alone, but more positive effects on health than being fed formula alone.
3. Being fed breast-milk and formula confers more positive effects on health than being fed an insufficient amount of breast-milk alone.
4. Regularly driving an SUV (say, 25+ miles per day) has non-negligible effects on the levels of pollution.
5. The pollution from regularly driving an SUV has non-negligible negative effects on the health of the persons exposed to the pollution.
6. And, the pollution from regularly driving an SUV makes a non-negligible contribution to anthropogenic global warming (AGR).
7. At a minimum, AGR will have very negative effects on the health of people living in regions likely to end up underwater as a result.

For a given set of scientific conclusions (which you’re welcome to call “knowledge” or “well-supported hypotheses” depending on your epistemic druthers), what ought non-scientists to do with them? Are individuals obligated to take certain kinds of actions based on scientific conclusions? Are individuals obligated even to take these conclusions into consideration when choosing a course of action? Are policy makers obligated to impose policies, in the light of these conclusions, to nudge (or coerce) individuals to act in certain ways rather than others? Are policy makers obligated to create the conditions where certain of the choices “supported” by the scientific conclusions are available to individuals? Are policy makers obligated to make sure the scientific conclusions in question are made widely available, and in a form non-scientists can understand?
All of these possibilities stand (or fall) based on more general assumptions about what we owe others, what “society” (here represented by the policy makers) owes its members, what we owe ourselves, and what kind of claims to freedom we ought to have even in the face of interests that may be harmed if we make certain choices rather than others.
The DHHS ad campaign advocating breast-feeding at least suggests that the important obligation to watch is the mother’s obligation to the current and future health of her infant. In other words, because mothers have this special obligation to their infants, they ought to feed their infants breast-milk — even if this requires sacrificing other interests (like earning enough to pay the bills, or getting a full night’s sleep, or whatever).
The current and future health of the infant is a good (at least to that infant). Is the mother the only one with an obligation to sacrifice other interests for that good? (If so, why?) If the goal is to secure the good of the current and future health of the infant, are there other parties DHHS ought to be trying to reach in advocating breast-feeding — for example, employers, who could provide accomodations for lactating mothers to pump, or on-site infant daycare and work breaks to enable breast-feeding , even though this would likely come with an economic cost?
Indeed, if the point is to secure the good of the current and future health of the infant, should DHHS be advocating to reduce other potential harms to that health — like the pollution and the contribution to AGR that comes from regularly driving an SUV?
Here, there’s an interesting asymmetry between the two cases. On the one hand, perhaps mothers have special duties to their infants that flow, at least in part, from their special capacities — here, to lactate. It’s more likely that the mother who just gave birth to the infant will be able to provide the good of breast-milk than will some random stranger off the street (given, especially, that the random stranger might be male). It’s true, not every mother gives birth to her infant (and some newborn infants lack mothers, for a variety of reasons), and that giving birth is not a guarantee that one will be able to produce a sufficient quantity of breast-milk for the infant one has borne. Still, more often then not the mother is the one most likely to have access to the breast-milk from which her infant could benefit. The flip side of this “special relationship” between mother and infant is what I think is a pretty common assumption made by the stranger on the street that the infant has no special claim on him or her. “I didn’t bring that baby into the world,” asserts the stranger, “so I have no special responsibility to secure the means necessary to improve its current and future health.”
(Is the potential employer essentially a stranger on the street in terms of responsibilities here?)
On the other hand, in the SUV-driving case, we are talking about a potential harm that is distributed fairly indiscriminately. You’re not just sharing tail-pipe emissions (and their effects downstream) with your nearest and dearest; you’re sharing them with the whole community. While we may have special obligations to help certain individuals, are we only bound by special obligations not to harm certain individuals? Do we have a general obligation to avoid doing harm to others, no matter what our relationship to them might be?
If I’m an infant, it may be that not just anybody can provide me with the breast-milk that would serve my needs. However, anyone with an SUV may have the means to harm my health. If my health is really a good worth securing, ought policy makers to attend just as closely to the harms to which I’m subjected (applying appropriate information, encouragement, and shame to the people exposing me to those harms) as the benefits (like breast-feeding) which would help secure that good?
Here’s another way of asking the question: Why are we more inclined to support free exercise of personal choice when it comes to what people drive than when it comes to what’s in their babies’ bottles?
(Arguably, many of the health effects of both breast-milk and pollution/AGR are downstream a ways — it doesn’t seem to me that people’s different responses to these two cases are primarily due to one involving a longer causal chain than the other.)
There really is a difference in how people seem to approach the ethical obligations (and the relative importance of autonomy) in these two kinds of cases. But I still feel like there’s something I’m missing as to what this difference tells us — either about our actual obligations, or about the ways the people reacting differently to these two cases are prioritizing various interests.
What am I missing?
For the record, I don’t think the difference turns at all on the state of our scientific knowledge about either case. Scientific knowledge can’t (at least in general) tell you what your interests are or what goals you should value, although such knowledge may be helpful in working out whether you can achieve all the goals you want to (and what strategies you might take to achieve your goals). Even if there were no dispute about the assumptions I made for the sake of argument, it seems people would still have different assessments of the moral imperatives in the two scenarios. We need to get to the differences in the ethical assumptions in the two cases to unravel the different judgments they seem to provoke.