Beverly Erlebacher writes
And a family as apparently innocuous as the Umbelliferae (or whatever it
is these days) full of tasty veggies and herbs like celery, dill, parsley,
carrots, fennel, etc, includes poison hemlock of which a really small amount
can kill an adult. And while many seeds of this family are used as
flavourings (dill, caraway, anise, cumin, cariander and many more),
carrot seeds can cause miscarriage.

=======
Stewart Robert Hinsley schreef
I never thought of Umbelliferae as innocuous; at a guess it contains 2
of the 3 most toxic plants in the British flora (hemlock and water
dropwort; the 3rd would be deadly nightshade).
--
Stewart Robert Hinsley

+ + +

Around here the Umbellifer with the most fearsome reputation by far is
Heracleum mantegazzianum (US: Giant Hogweed), which frequently puts people
in hospital and is potentially lethal, without anybody taking a bite

See eg

http://www.wa.gov/agr/weedboard/weed_info/hogweed.html

On the other hand it does make a nice story when connected to treating
psoriasis with another of the Umbellifers
PvR