A site that lists the plants sensitive to black walnut trees is
https://www.bachmans.com/tipsheets/Woodies/BlackWalnuts_print.cfm .
With the right plants, I don't see why it couldn't make a good guild
addition. It has tremendous food/medicinal/building properties.
In what I have read, their isn't a direct respiratory effect on humans
except that the pollen in the male flower parts (catkins) is a common
allergen- just as grasses, acacias, dust and mold can be. I would note
when asthma flares up, and see if the black walnuts are in bloom. I
grew up with asthma and ate a lot of California Black Walnuts (Juglans
californica) without ill effect (swimming in LA smog was the culprit).
Even the effect on fish results in the slowing of breathing, the
opposite of asthma. I have used mullein and chamomile tea for my
child's asthma with great results. I am going to try raspberry tea as
it has anti-spasmodic effects, but we haven't had any problems for a
long time now. Feel free to email me if you want more information.