What would you do about damage to your property when theres nothing you can do?

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We got new neighbors about 1 and a half years ago, since then they have not been too much of a problem, but recently they have inserted a range hood in next to their Barbecue (on our boundary) to exhaust barbecue fumes as well has the heat into our property causing our plants to die as well as making us ill. We have gone to council, but they will not do anything, they say that it is legal and will not take any action. We have tried talking to them and asking them not to use it as well as come over to our side and see what damage it is causing, again they are not interested in discussing this. What would you do? What suggestions can you make?