Proposed Registration Decision for the New Active 

Ingredient Hexanoic Acid 

PC Code: 041201 
1.0 Summary 

This document announces that the Environmental Protection Agency (EPA) has completed its 

eva luation of the new biochemical active ingredient, hexanoic acid, and has concluded that it 

meets the regulatory and safety standards under the Federal Insectic ide, Fungicide and 

Rodenticide Act (FIFRA). 

One product is proposed for registration under Section 3(c)(5) of FIFRA: an end-use product 

(EP), BG-Sweetscent, containing hexanoic acid for non-food use. Hexanoic acid is intended for 

formulation into end-usc products that attract a broad range of mosquitoes (by mimicking odors 

emitted from human skin) into traps where they die, when used in accordance with label 

directions. 

Hexanoic acid, also known as caproic acid, is a member of a group of short-chained linear fatty 

acids (i.e., heptanoic, octanoic acid). It is a fatty acid found naturally in many plant and animal 

fats and is structurally similar to octanoic acid, which has already been assessed by the Agency. 

As a result of its natural occurrence in various plant and animal fats and oils, including coconut 

and palm oil, vanilla, and cow and goat's milk, in 1977, the Food and Drug Admi nistration 

(FDA) gave broad approval of fatty acid as an additive in foods. Included in that approval is the 

group of straight chain monobasic carboxyli c ac ids that includes hexanoic acid. Hexanoic acid is 

considered by FDA to be GRAS as a synthetic flavoring food additive (2 1 CFR 172.51 5) and has 

been approved for use in washing and peeling of fruits and vegetables (2 1 CFR 172.3 15). 

Hexanoic acid is currently used as an additive in a wide range of foods including, nuts, cocoa, 

dairy products, savory vegetables, and meats. Hexanoic acid has also been determined to be 

exempt from the requirement for a tolerance by the Agency when used as a fragrance agent (40 

CFR 180.940) with an upper limit for use in pesticide formulations of l 00 ppm. 

As a biopcsticide, hexanoic acid is classified as an attractant for mosquitoes. The smell of 

hexanoic acid is that of goat cheese or sweat but in combination with lactic acid and ammonium 

bicarbonate effectively attracts mosquitoes. Attractants, as well as repellents, have specific 

stimulatory effects on insect receptor neurons and can be seen as modulators of mosquito odorant 

receptor acti vity (olfactory receptor neurons), stimulating olfactory and gustatory receptors on 

insect antenna. 

The proposed product, BG-Sweetscent, is enclosed in a Tyvek® sachet as a mixture of 

ammonium bicarbonate and porous polymer pellets that are loaded with lactic and hexanoic acid. 

The Tyvek~ membrane protects the ammonium bicarbonate and polymer pellets from water and 

allows the volatile compounds to diffuse out. The porous polymer pellets act as a controlled 

release mechanism for the volatile compounds, lactic and hexanoic acid, providing a non-liquid 

presentation of the chemicals. Ammonium bicarbonate is the precursor for ammonia as it slowly 

decomposes into ammonia, carbon dioxide, and water at ambient temperatures. 

The lure is proposed to be used in various types of mosquito traps and is replaced after 8 

weeks of use. The users are instructed to NOT open the enclosed sachets thus preventing 

exposure to the product. Rather, users are instructed to insert the sachet into a pesticide device 

(trap) and therefore, use of the product does not result in direct exposure to the user. The 

Tyvek® sachet is designed to release the scent of hexanoic acid slowly over a period of 8 

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weeks as a lure for mosquitoes. This slow-release of hexanoic acid vapor will result in very 

low concentrations in the outdoor air surrounding the mosquito trap. 

2.0 Background 

The Biochemical Classification Committee (BCC) classified hexanoic acid as a biochemical 

pesticide due to its natural occurrence. history of exposure to humans and the environment 

without toxicity. and its nontoxic mode of action to the targeted pest. The use or hexanoic acid is 

similar to previously registered insect attractants in that it is used as a selective attractant to 

manage specific insects (i.e .. mosquitoes). It is delivered from a stationary trap, as a slow release 

voltile compound that attracts the targeted insect into the trap where they naturally die. 

On April 20, 2015, EPA received an application from Teclu10logy Sciences Group, Inc .. on 

behalf of Biogents AG for the registration of a non-food use mosquito attractant containing the 

proposed new active ingredient, hexanoic acid. On August 25. 20 15. EPA announced receipt of 

an application to register a product containing the proposed new active ingredient. hexanoic acid 

(80 FR. umber 164. pages 51560- 51561 ). No comments were received in response to the 

announcement (Document ID: EPA-HQ-OPP-20 15-0547). 

3.0 Evaluation 

In eq1luating a pesticide rcgi tration application. the EPA ass~sscs a wide \aricty of pesticidespecific information in<.:luding " ·here and ho" the pesticide is used. enYironmental fate (i.e .. 

" ·hat happens to the pesticide once it" s applied), and toxicity studies (i.e .. cllects on humans and 

other non-target organisms) to uctermine the likelihood or ath·e rsc effects (i.e .. risk) from 

exposures assoc iated with the proposed use or the prouu<.:t. Risk assessments arc ucwlopeu to 

cn1luate the environmental fate of the compound as well as ht)\\ it might affcc..:t a \\'ide range of 

non-target organisms including humans and terrestrial and aquatic " ·ildlifc (plants and animals). 

Based on these assessments. EPA evaluates and appro\'es language (()reach pesticide label to 

ensure that the directions for use and safety measures arc appropriate to mitigate potential risk. In 

this way. the pesticide's label helps to communicate essential limitations and mitigation!:> that arc 

necessary for public safety. It is a riFRA ,·iolation to use a pestieiue in a way that is inconsistent 

" ·ith the label. 

The human health and environmental risk assessments (including an endangered species 

assessment) supporting this proposed decision as well as the draft labeling can be found in the 

regulatory docket (Document ID: EPA-HQ-OPP-20 15-054 7). 

3.1 Assessment of Risk to Human Health 

EPA requires a wide range of studies in order to assess a pesticide. The toxicological database is 

considered complete for characterizing hazard and assessing risk from hexanoic ac id for nonfood uses. The applicant has adequately addressed all data requirements for the proposed use or 

hexanoic acid with scientific rationales supported by data/information from open literature. 

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3.1.1 Toxicity 

The avai lable data/information indicate that technical-grade hexanoic acid is acutely toxic 

(c lassified as Toxicity Category I - signal word Danger) for primary eye irritation and primary 

skin irritation routes of exposure. ln terms of acute inhalation exposure, the LC50 was > 1.368 

mg/L, which corresponds to an EPA Toxicity Category Ill for the inhalation route. For acute 

dermal exposure, the compound is classified as Toxicity Category IV. Inforn1ation submitted in 

support of hexanoic acid show that it is not a dermal sensitizer. 

Acute toxicity data requirements for the end use product were addressed with rationales based on 

the fact that there will be no exposure to the end use product. Eye contact is not anticipated when 

using and/or handling the product as directed on the proposed product label since the active 

ingredient is packaged into granules that are contained in a heat-sealed Tyvek sachet (designed to 

not rip or tear) and furthe r placed inside a trap. Likewise, the toxicity category for eye irritation 

of the EP, would not be expected to be higher than toxicity category I of the technical material 

because of the lower concentration of hexanoic acid in the end-use product (8.82 % w/w) 

compared to that of hexanoic acid as its active ingredient (98 % w/w). Therefore, given the lack 

of exposure that is expected, proposed precautionary labeling commensurate with Caution is 

appropriate. 

Subchronic oral toxicity data requirements were satisfied through information from the open 

scientific literature. Two dietary feeding studies were assessed and found to collectively satisfy 

the subclu·onic oral data requirement. No adverse effects were noted in either study as a result of 

exposure to hexanoic acid. 

In a prenatal developmental toxicity study on octanoic acid, a fatty acid closely related to 

hexanoic acid, the No Observed Adverse Effect Level (NOAEL) for developmental toxicity is 

I, 125 mg/kg/day, which is the maternal Lowest Observed Adverse Effect Level (LOAEL) for 

reduced body weight gain and respiratory effects that included rales and dyspnea. Fetotoxicity 

was observed at 1,500 mg/kg in the form of a reduced number of live pups on postnatal day 6 

compared to the controls. 

Subchronic dermal and inhalation toxicity data requirements were waived based on lO\V 

likelihood of exposure via these routes. More detail on anticipated exposures to hexanoic acid 

resulting from the proposed use pattern is provided below. 

3.1.2 Exposure and Risk 

The proposed use of hexanoic acid is not likely to result in significant levels of oraL dermal or 

inhalation exposure due to a combination of the product fonnulation and packaging. The 

hexanoic acid is infused into porous polymer pellets which are then enclosed in a TyvekOi: sachet. 

The Tyvekqy membrane protects the polymer pellets from water and allows low levels of the 

volatile hexanoic acid to slowly diffuse out over a period of 8 weeks. These sachets are placed 

inside a trap device further limiting the potential for human exposure. 

As mentioned earlier, hexanoic acid has been approved as a food additi ve, for use in food 

processing and can be found as a natural component in many animal and plant fats/oils. These 

exposures are considered safe by FDA. However, the use of hexanoic acid as a mosquito 

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attractant is not considered a food use and oral exposures to hexanoic acid as a result of residues in 

food or drinking water from this pesticidal use are not expected. 

Dermal contact ·with the polymer pellets is not anticipated since they are enclosed in Tyvek k 

sachet. In addition, the extent of contact with the sachets is limited to the placement of the 

product in a trap and removal of the spent sachet e ight weeks later further limiting the negligible 

potential for dem1al exposure, 

The slow-release of hexanoic acid vapor will result in very low air concentratio ns in the o utdoor 

air immediately surrounding the trap. No signifi cant repeat inhalation exposure to the active 

ingredient as a gas. vapor or aerosol is anticipated given the low levels being re leased from the 

polymer pellets and the rapid dilution of these low levels in ambient o utdoor a ir. Further. to 

provide additional context, the maximum anticipated level of hexanoic acid in the proposed endusc product is 34 ppm which is significantly less than the maximum allowable limit for its usc as 

a fragrance of 100 ppm. Considering that the product is designed to release the 34 ppm over the 

course of 56 days the Agency believes that exposures from this use pattern would be 

substanti ally lower than approved fragrance exposures. 

Based on the low potential for occupational, residential handler or bystander exposure via the 

oral. dem1a l and inhalation pathways, the Agency has determined that a quantitati ve risk 

assessment is not needed for hexanoic acid and that risks of adverse effects to humans are not 

anticipated based on the proposed use pattern. 

3.2 Ecological Risk Assessment and Conclusions 

The available data is adequate to assess the ecological effects of hexanoi c acid and to conduct an 

ecological risk assessment. All non-target organism toxicology and enviro nmenta l fate data 

requirements (per 40 CfR 158.2060) have been satisfied through citation of data/information 

from the open scientific literature. In conducting its risk assessment. the structural similarity of 

hexanoic acid to heptanoic, octanoic and no nanoic acid served as the basis for allowing the 

Agency to usc toxicology and ecological data and assessments from these related compo unds as 

surrogate data (USEPA. 2009). 

As part of the Agency's registration review decision for octanoic acid in 2009, a registered 

fatty ac id closely rel ated to hexanoic acid, the Agency conducted a review o f the scientific 

databases and other relevant information and waived a ll generic ecotoxicity and environmental 

fa te data requirements fo r this chemical. Fatty acids normally are metaboli zed. forming 

simple compo unds that serve as energy sources and structural components used in a ll living 

cells. The Agency determined that an ecological risk assessment was not needed as part of this 

decisio n (USEPA. 2009). 

A review of the available scientific literature to r hexanoic acid indicated that hexanoic acid is 

practi call y non-toxic to fish and aquatic invertebrates. 

In addition to the lack of toxicity to non-target organisms. the potential for ecological exposure 

is low since the product is infused into a polymer pellet which is enclosed in Tyvek 1i sachet 

which is placed inside a trap device further limiting the potential exposure. There fo re, contact 

with and contamination of surface water, ground water or soil is highl y unlike ly from the 

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proposed pesticidal use of hexanoic acid. Further, fatty acids such as hexanoic acid have been 

determined to be biodegradable and are found extensively in the environment from natural sources 

making any unlikely incremental increase from the pesticidal use of no concern. 

The Agency has also determined that most non-target insects, including honeybees, are not 

like ly to be exposed to hexanoic acid at significant levels when used as a mosquito lure since 

they are not likely to be attracted to the scents targeted at the unique feeding patterns of 

mosquitoes. Bees in particular are attracted to floral scents while hexanoic acid has a pungent 

odor similar to sweat or strong cheese, which does not entice bees. Further, as described 

earlier. incidental inhalation exposures to non-target organisms are expected to be low given 

the low levels being released from the polymer pellets, the rapid dilution of these low levels in 

ambient outdoor air, and the extensive presence of naturally occurring hexanoic acid in the 

environment. 

Given the lack of toxicity to non-target organisms and the low potentia l for exposure as a 

result of the proposed pesticidal uses. the Agency does not anticipate risk of adverse impacts 

to non-target organisms as a result of the proposed use pattern. 

The Agency has evaluated the potential risk of hexanoic acid exposure to endangered/threatened 

species and based on the lack of toxicity to non-target organisms and the low potential for 

exposure described above, the use of BG-Sweetscent as a mosquito attractant trap will have "No 

Effect" on terrestria l enda ngered/threatened species or their designated critical habitats, as 

listed by the U.S. Fish and Wildlife Service (USFWS) and the National Oceanic and 

Atmospheric Administration (NOAA). The use patterns (enclosed trap) and resulti ng low 

potential exposure to aquatic systems also show a finding of"No Effect" to 

enda ngered/threatened aquatic species or their designated critical habitats. In addition to low 

exposure potential resulting from the proposed pesticidal use, the Agency also acknowledges the 

natural occurrence of hexanoic ac id in the environment and its rapid decomposition. 

4.0 Alternatives 

As with most insect attractants, hexanoic acid is expected to generally reduce the amount of 

conventional insecticides required for management and eradication of targeted insect populations 

since no conventional pesticides are necessary to lure and trap the mosquitoes. 

5.0 Benefits 

Biopesticides are pesticides derived from such natural materials as animals. plants. bacteria. and 

certain minerals. Biochemicals, a class of biopesticides to which hexanoic acid belongs, 

generally compare favorably to currently registered conventional a lternati ves from a toxicity and 

environmental standpoint because they arc naturally-occurring substances (or substances 

structurally-similar and functionally identical to naturally-occulTing substances) with a history of 

exposure to humans and the environment demonstrating minimal toxicity and a nontoxic mode 

of action to the target pest(s). Benefits of biochemical pesticides as compared to conventional 

pesticides typically inc lude lower toxicity profiles for humans and non-target organisms, and 

faster degradation in the environment. Additionally. as outlined above. hexanoic acid has the 

potential to reduce the amount of more toxic conventional pesticide applications to manage or 

eradicate mosquitoes. 

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5.0 Public Comments 

On August 25, 2015, EPA published a notice of receipt of an application in the Federal Register 

to register an end use product (BG-Sweetscent 9%) containing a proposed new active ingredient. 

Hexanoic Acid (80 FR. umber 164. pages 5 1560- 5161) and announced a pub I ic comment 

period of 30 days . o substanti ve comments ' ere received. 

6.0 Proposed Regulatory Decision 

The hexanoic acid database is comprised of studies and info rmation that meet the data 

requirements for and support the labeled uses of hexanoic acid. In considering the assessed risk 

to human health and the environment, the EPA concludes that hexanoic acid meets the regulatory 

standard under the Federal Insecticide, Fungicide. and Rodentic ide Act (FIFRJ\). Therefore. the 

EPA is proposing to grant the unconditional registration of the hexanoic acid pesticide products 

under FIFRA section 3(c)(5). 

One end-use product. BG - Sweetscent (8.82% hexanoic ac id). is being proposed lo r registration 

as a non-food use pesticide for use as a lure/attractant targeting mosquitos. The product is 

formulated into porous polymer pellets which are enclosed in Tyvek 19 sachets. The sachets are 

placed in mosquito traps where the insects are lured and die. 

The human health and ecological risk assessments supporting this decision as \veil as the draft 

labeling remain available in the regulatory docket (Docket 10 EPA-HQ-OPP-20 15-0547). 

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