UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

Date: 3/5/13 

MEMORANDUM 

OFFICE OF 

CHEMICAL SAFETY AND 

POLLUTION PREVENTION 

SUBJECT: Ancymidol. Registration Review Preliminary Risk Assessment. 

PC Code: 1 08601 DP Barcode: D408396 

Decision No.: 474083 Registration No.: 10163-277 

Petition No.: NA Regulatory Action: Registration Review 

Risk Assessment Type: Single Chemical Case No.: 3017-1 Aggregate 

TXRNo.: NA CAS No.: 12771-68-5 

MRIDNo.: NA 40 CFR: NA 

FROM: DonnaS. Davis, Risk AssessorCJ:;[Jtt~~l-(:)_ Health Effects Division (7509P) 

THROUGH: Michael 

Risk Assessment 

Metzger, 

Br

Chief 

anch VII ~~ ~ /) (} !\ f ~ Health Effects Division (7509 

TO: Christina Scheltema, Risk Manager 

Tracy Perry, Team Leader 

Patricia Parrott, Chief 

Risk Management and Implementation Branch III 

Pesticide Re-Evaluation Division (7508P) 

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Ancymidol Registration Review Preliminary Risk Assessment 

Ancymidol is a plant growth regulator. Ancymidol is a Type liB gibberellic acid inhibitor and is 

used to prevent elongation, or "legginess" in ornamental plants. The Biological and Analysis 

Division (BEAD) has indicated that no more than 20 lbs total of ancymidol are used per year in 

the U.S. (BEAD Chemical Profile for Registration Review, Rafael Prieto, 11/19/1 0). Ancymidol 

is formulated as a soluble concentrate or liquid currently registered for uses in nurseries, 

greenhouses, shadehouses and interiorscapes. Ancymidol appears to be predominantly applied to 

containerized bedding ornamental plant plugs in greenhouse propagation settings (i.e., indoors under 

glass). There are also some drench type applications in greenhouses and small scale treatments of 

ornamental seeds. There are no agricultural or residential uses of this active ingredient. 

Given the use pattern, exposure is limited to workers applying ancymidol. Workers are expected 

to be exposed only through the dermal and inhalation routes of exposure. 

A 21-day guideline dermal toxicity study conducted in the rabbit showed no dermal irritation or 

systemic toxicity after repeated exposure up to the limit dose of 1000 mg/kg/day. Therefore; the 

Agency concludes that ancymidol does not pose a dermal risk. 

Exposures via the inhalation route are expected to be acute in nature and exceptionally low given 

the registered application rates and the low total poundage applied in the U.S. Ancymidol has 

low acute inhalation toxicity. In light of the extremely low application rates, the Agency has 

considered the available hazard information and finds nothing in the database or in the literature 

that would suggest that this active ingredient is sufficiently potent to raise a concern at such low 

exposure levels. Based on the limited use pattern, the minimal inhalation exposure, and the lack 

of evidence that ancymidol displays significant toxicity by the inhalation route; the Agency does 

not believe that this active ingredient poses an inhalation risk. 

No additional exposure or hazard information are required to support the registration review of 

ancymidol. Quantitative risk assessments are not required for this active ingredient and the 

Agency does not believe that the current registered uses of ancymidol pose a human health risk 

of concern. 

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