Bodily harm is not the only form of harm for which one may be liable. Repeated dispersal of unwanted waste upon other's property could be considered property damage, even if the waste cannot or has not yet caused exposure related medical conditions upon their person.
In an alternate legal context, a society might decide that proving an ash residue repeatedly collected on your property matches ash repeatedly emitted by a factory is sufficient grounds for property damage litigation without requiring you to also prove bodily harm. However, this would raise costs on industry by requiring them to be located further from residential areas.
Different societies will arrive at different tradeoffs and balances on these issues through the use of non-market forces, which will influence the incidence of negative externalities as much as market forces.