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The Environmental Protection Agency (EPA or the Agency) has completed the human health and environmental risk assessments for propylene glycol and dipropylene glycol and is issuing its risk management decision and tolerance reassessment. The risk assessments, which are summarized below, are based on the review of the required target database supporting the use patterns of currently registered products. As a result of this review, EPA has determined that products containing propylene glycol and dipropylene glycol alone are eligible for reregistration.
Products containing propylene glycol and dipropylene glycol in combination with other active ingredients will be reregistered only when all of the active ingredients have been determined to be eligible for reregistration. That decision is discussed fully in this document.
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As active ingredients, propylene glycol and dipropylene glycol are formulated primarily as pressurized liquids and ready-to-use solutions. Propylene glycol is used in air sanitization and hard surface disinfection and dipropylene glycol is used in air sanitization. Pest (fleas, mites, red lice, and various bacteria and viruses) control for pets (cats, dogs, and birds) is also a major active use for propylene glycol. As an inert ingredient, propylene glycol is formulated into end-use agricultural and antimicrobial pesticide products whereas dipropylene glycol is formulated into pesticide products for use in agricultural settings. Products containing propylene glycol and dipropylene glycol in combination with other active ingredients will be reregistered only when all of the active ingredients have been determined to be eligible for reregistration. This document addresses the exposures and risks from the use of these pesticides as both active and inert ingredients in pesticide products.
The Agency has concluded that the FQPA Safety Factor for propylene glycol and dipropylene glycol should be removed (equivalent to 1X) because there is no pre- or post-natal evidence of increased susceptibility for infants and children following exposure to either propylene or dipropylene glycol.
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I. CHEMICAL OVEVIEW
A. Regulatory History
Propylene glycol and dipropylene glycol were first registered in 1950 and 1959, respectively, by the FDA for use in hospitals as air disinfectants. At one point, there were approximately 190 pesticide chemical companies having active propylene or dipropylene glycol registrations. Many of these registrations were canceled over the years and more recently, the majority of the remaining producers of propylene and dipropylene glycol formulated pesticide products are being represented by a consortium called the CSPA (Consumer Specialty Products Association) Glycols Joint Venture. The member companies currently represented by this consortium are:
Amrep, Inc., Beaumont Products, Inc., Chase Products, MEDO/SOPUS Products, Reckitt Benkiser, Inc., S.C. Johnson & Son, Inc., Wellmark International, and Waterbury Companies, Inc.
B. Chemical Identification
1. Propylene Glycol: Common Name: Propylene Glycol Chemical Name: 1, 2-Propanediol or 1,2-hydroxypropane Chemical family: None Case number: 3126 CAS registry number: 57-55-6 OPP chemical code: 068603 Empirical formula: C3H8O2 Molecular weight: 76.00 g/mol Trade and other names: Propylene glycol Specific Gravity: 1.038
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General Toxicity Observations
Upon reviewing the available toxicity information, the Agency has concluded that there are no endpoints of concern for oral, dermal, or inhalation exposure to propylene glycol and dipropylene glycol. This conclusion is based on the results of toxicity testing of propylene glycol and dipropylene glycol in which dose levels near or above testing limits (as established in the OPPTS 870 series harmonized test guidelines) were employed in experimental animal studies and no significant toxicity observed.
A review of the available data has shown propylene glycol and dipropylene glycol to be negative for carcinogenicity in studies conducted up to the testing limit doses established by the Agency; therefore, no further carcinogenic analysis is required.
Propylene glycol and dipropylene glycol were tested for mutagenic or genotoxic potential and found to be negative in a battery of studies: a bacterial gene mutation assay using Salmonella typhimurium, and in vitro Chinese hamster ovary (CHO) mutation assay, an in vitro Chinese hamster ovary (CHO) chromosomal aberration assay and an in vitro sister chromatid exchange assay.
2. FQPA Safety Factor
The FQPA Safety Factor (as required by the Food Quality Protection Act of 1996) is intended to provide an additional 10-fold safety factor (10X), to protect for special sensitivity in infants and children to specific pesticide residues in food, drinking water, or residential exposures, or to compensate for an incomplete database. The FQPA Safety Factor has been removed (i.e., reduced to 1X) for propylene glycol and dipropylene glycol because there is no pre- or post-natal evidence for increased susceptibility following exposure. Further, the Agency has concluded that there are no endpoints of concern for oral, dermal, or inhalation exposure to propylene glycol and dipropylene glycol based on the low toxicity observed in studies conducted near or above testing limit doses as established in the OPPTS 870 series harmonized test guidelines.