Paclobutrazol has never been proven to be a carcinogen. daminozid (flower dragon) has.
This is not strictly true. The EPA states there is no data meaning that there is an unknown quantity associated to the use of PBZ. I.e.
_II. Carcinogenicity Assessment for Lifetime Exposure
Substance Name — Paclobutrazol
CASRN — 76738-62-0
This substance/agent has not undergone a complete evaluation and determination under US EPA's IRIS program for evidence of human carcinogenic potential.
And
_I.B. Reference Concentration for Chronic Inhalation Exposure (RfC)
Substance Name — Paclobutrazol
CASRN — 76738-62-0
Not available at this time.
And:
__I.A.3. Uncertainty and Modifying Factors (Oral RfD)
UF — Based on a subchronic exposure study, an uncertainty factor of 1000 was used to account for inter- and intraspecies differences and for the insufficient duration of the study to fully assess chronic effects.
MF — None
Seems to me there is a heap of things they don't know and a few they do know.
The thing is with a lot of chems some were once deemed safe and used for years before problems arose and it became apparent that what was thought safe was actually unsafe for use (eg. Agent Orange, DDT etc). There has also been no combustion tests or withholding period tests re cannabis with PBZ so really what you have is one big unknown factor.
http://www.epa.gov/iris/subst/0182.htm Oh and its "Daminozide" which is listed as a "probable human carcinogen" and banned for use in any consumable crop in1989. Flower Dragon contains Daminozide as does Phosphoload and Top Load. Either way only a scum bag no nothing grower would use these products now knowing what they contain.