Bronopol is a synthetic compound commonly used as a preservative in cosmetic and personal care products. It is effective in preventing the growth of bacteria, fungi, and yeast, thereby extending the shelf life of formulations. Bronopol functions by releasing small amounts of formaldehyde, which acts as an antimicrobial agent.
Due to its broad-spectrum efficacy, it is often found in products such as lotions, creams, and shampoos. Understanding its properties and regulatory status is essential for both formulators and consumers concerned about the safety and effectiveness of cosmetic ingredients.
CAS Number: 52-51-7
Molecular Formula: C3H6BrNO4
Synonyms:
- bronosol
- 2-bromo-2-nitro-1,3-propanediol
- 2-bromo-2-nitropropane-1,3-diol
Uses of Bronopol in Cosmetics
Functional role in cosmetics:
- Bronopol is used as a preservative agent in cosmetics.
Other uses:
- It is also used as a surfactant.
Cosmetic Products Containing Bronopol
Recent products using Bronopol in their cosmetic formulations
- Neutrogena Hydro Boost Water Gel
- L’Oréal Paris Elvive Shampoo and Conditioner
- Clairol Nice’n Easy Hair Color
- Garnier Fructis Shampoo and Conditioner
- Aveeno Daily Moisturizing Lotion
- Eucerin Aquaphor Healing Ointment
- Olay Regenerist Micro-Sculpting Cream
- The Body Shop Body Butters
- Pantene Pro-V Shampoo and Conditioner
Top companies using Bronopol in their cosmetic products
- Neutrogena
- L’Oréal
- Clairol
- Garnier
- Aveeno
- Eucerin
- Olay
- The Body Shop
- Pantene
Regulatory Considerations for Using Bronopol in Cosmetic Formulations
Few regulatory considerations are to be taken into account before using Bronopol as an ingredient. Given below is the list of those regulations:
FDA Requirements: 2-Bromo-2-nitro-1,3-propanediol is permitted as an indirect food additive for use only as a component of adhesives. It is limited to use as an antibacterial preservative.
FIFRA Requirements: Bronopol is listed under FIFRA’s pesticide reregistration program on List B, indicating higher concern compared to List C and D pesticides. It is classified as a herbicide and antimicrobial, with a Reregistration Eligibility Decision (RED) approved in September 1995. EPA has determined that some/all uses of Bronopol are eligible for reregistration under updated safety standards.
Status Regulation (EC): Regulation EC 2002/2076 applies to Bronopol.
REACH Registered Substance: Bronopol is registered under REACH with active status as of December 1, 2022.
New Zealand EPA Inventory of Chemical Status: Bronopol is approved with controls under HSNO Approval HSR003563.
The Australian Inventory of Industrial Chemicals: Bronopol is listed as 1,3-Propanediol, 2-bromo-2-nitro- in the Australian Inventory of Industrial Chemicals.
Alternatives of Bronopol and Comparative Analysis
Given below is the list of alternative ingredients that can be used in place of Bronopol in cosmetic formulations:
- Phenoxyethanol
- Ethylhexylglycerin
- Benzyl Alcohol
- Caprylyl Glycol
- Chlorphenesin
Comparative analysis of Bronopol alternative ingredients:
| Ingredients | Strengths | Limitations | Efficacy | Cost | Stability | Compatibility | Safety |
| Phenoxyethanol | Broad-spectrum antimicrobial activity Effective preservative for cosmetics and personal care products Stable under a wide range of pH and temperature conditions Less sensitizing compared to bronopol | Potential irritation in high concentrations Not effective against all fungal strains (may require combination with other preservatives) | High as a preservative | Moderate | High (stable in various formulations) | Good with most cosmetic ingredients; requires pairing for full-spectrum protection | Generally safe but can cause irritation in sensitive skin |
| Ethylhexylglycerin | Boosts efficacy of other preservatives (synergistic effect) Mild antimicrobial properties Improves skin feel and acts as a humectant | Not effective as a standalone preservative Requires combination with stronger antimicrobials | Moderate as a preservative booster | Moderate | High | Good with most preservatives and cosmetic bases | Safe and well tolerated |
| Benzyl Alcohol | Natural origin (found in fruits and teas) Effective antimicrobial properties, especially against bacteria Widely used in natural and clean beauty formulations | Can cause irritation or sensitization at high concentrations Limited efficacy against fungi (requires combination with other agents) | Moderate as an antimicrobial agent | Low to moderate | Moderate (can oxidize over time) | Good in natural formulations; limited for sensitive skin | Potential allergen at higher concentrations |
| Caprylyl Glycol | Provides antimicrobial activity and enhances preservation systems Acts as a humectant, improving skin hydration Compatible with most cosmetic bases | Not effective as a standalone preservative Requires combination with stronger antimicrobials | Moderate as a preservative booster | Moderate | High | Good with most preservatives | Safe and non-irritating |
| Chlorphenesin | Broad-spectrum antimicrobial activity Effective against bacteria, fungi, and yeasts | Potential irritant for sensitive skin Not suitable for leave-on products targeting sensitive skin | High antimicrobial properties | Moderate | High | Good with most cosmetic bases | Requires careful concentration management due to sensitization risks |
How Bronopol Works in Formulations
Bronopol is widely used in cosmetics as an effective preservative, thanks to its broad-spectrum antimicrobial activity. It helps protect formulations from microbial contamination, ensuring product safety and extending shelf life.
Ideal Concentration and Benefits in Different Formulations
Shampoos and Cleansers
Bronopol is commonly included in shampoos and cleansers to prevent the growth of harmful microbes.
- Concentration: 0.01%–0.1%
- Benefit: Bronopol protects the product from a wide range of bacteria, fungi, and yeast. It also ensures the microbial stability of liquid personal care products.
Creams and Lotions
In creams and lotions, Bronopol helps extend the shelf life by preventing microbial contamination.
- Concentration: Typically below 0.1% to minimize irritation risks
- Benefit: Keeps products fresh by inhibiting microbial growth, making it ideal for moisturizers and other water-based products. It works well with various surfactants and solvents in emulsions.
Eye Makeup and Cosmetics
Bronopol is also used in eye makeup products to prevent microbial spoilage.
- Concentration: Kept low to avoid potential irritation
- Benefit: Ensures the safety of eye cosmetics, which are especially prone to contamination.
Compatibility with Other Ingredients
Bronopol is soluble in water and many organic solvents, making it versatile for liquid formulations. Stable across a wide pH range but may release formaldehyde over time, especially at higher pH. It may cause skin irritation or allergic reactions in sensitive individuals, therefore, patch testing is recommended.
Stability and Shelf Life
Bronopol remains stable when stored properly, but its performance can degrade if exposed to certain conditions.
- Shelf life: 12–24 months
- Best storage: Keep in a cool, dry place away from incompatible materials (e.g., high heat or moisture). Choose moisture and heat-resistant packaging to preserve efficacy and avoid contamination.
Formulation Challenges and Troubleshooting
Bronopol presents several formulation challenges due to its potential for irritation and formaldehyde release:
Formaldehyde Release
Bronopol can release formaldehyde over time, which may increase irritation risks and environmental concerns.
Solution: Use at low concentrations and ensure proper pH control to minimize formaldehyde release.
Skin Irritation
At higher concentrations, Bronopol may cause skin irritation or allergic reactions.
Solution: Limit use to concentrations below 0.1% and conduct patch testing for sensitive users.
Packaging Compatibility
Bronopol can corrode certain metals and degrade packaging materials over time.
Solution: Use compatible packaging materials like glass or HDPE to prevent degradation.
Regulatory Compliance
Ensure compliance with local regulations regarding maximum allowable concentrations and labeling requirements.
Solution: Consult regulatory guidelines for specific applications and regions.
Environmental and Sustainability Impact
Bronopol is a widely used antimicrobial agent in cosmetics, known for its effectiveness against bacteria, fungi, and yeast. Its use raises environmental and sustainability considerations:
Environmental Impact
- Water Pollution: Bronopol can be toxic to aquatic organisms due to its antimicrobial properties. However, it is generally used in small concentrations in cosmetics, minimizing its environmental impact.
- Carbon Footprint: The production of Bronopol involves chemical synthesis processes that contribute to greenhouse gas emissions. Sustainable manufacturing practices can help reduce its carbon footprint.
Sustainability
The sustainability of Bronopol depends on its production methods and disposal practices.
- Raw Materials: Bronopol is synthesized from nitromethane and bromine, which are not renewable resources. Greener synthesis methods could improve its sustainability.
- Energy Use: Manufacturing requires moderate energy input. Cleaner energy sources could reduce its environmental footprint.
- End-of-Life Impact: Bronopol decomposes into simpler compounds but may release formaldehyde, which can be harmful to the environment and human health.
Biodegradability and Toxicity
Bronopol is not readily biodegradable and can be toxic to aquatic life due to its antimicrobial properties.
Ammonia Toxicity: Not applicable. However, Bronopol releases formaldehyde, which can be toxic and irritating to humans and wildlife.
Eco-Friendly Alternatives
While Bronopol is effective, alternative preservatives may offer sustainable options:
- Phenonip: A blend of preservatives that can replace Bronopol in some formulations with potentially lower environmental impact.
- Ethylhexylglycerin: A natural preservative booster that enhances the efficacy of other preservatives, reducing the need for strong antimicrobials.
- Natural Preservatives: Derived from plants or natural sources, these alternatives can provide similar antimicrobial effects with lower ecological risks.
Bronopol Side Effects
Bronopol can decompose under alkaline conditions or elevated temperatures, releasing nitrite and small amounts of formaldehyde. These byproducts can interact with secondary amines or amides, potentially leading to the formation of nitrosamines, which are associated with cancer risk.
In the body, nitrosamines are metabolized by cytochrome P-450 enzymes, resulting in the formation of DNA adducts that may initiate carcinogenic processes. Additionally, formaldehyde is recognized as a carcinogen, with its toxicity linked to the saturation of formaldehyde dehydrogenase, which allows the accumulation of unmetabolized formaldehyde.
This compound can create cross-links between proteins and DNA and integrate into macromolecules such as DNA, RNA, and proteins, contributing to its toxic effects.
Potential Risks
Given below is the list of potential side effects associated with the use of Bronopol in cosmetics:
- Contact dermatitis, allergic
Symptoms
- Eye Exposure: May cause redness, stinging sensation, pain, or burns.
- Skin Exposure: May cause redness.
- Ingestion Exposure: May lead to sore throat or tingling sensation.
- Inhalation Exposure: May cause cough or sore throat.
Treatment
In case of eye contact, irrigate the affected eyes with running water for several minutes, keeping the eyes open. If the product is ingested, do not induce vomiting. Rinse the mouth thoroughly with water, but never give anything by mouth to an unconscious person and seek immediate medical attention.
For skin contact, rinse the affected area immediately with cold running water for at least 15 minutes, followed by thorough washing with soap and water. If necessary, the person should shower, change any contaminated clothing or shoes, and seek medical attention. In the event of inhalation, move the person to fresh air. If breathing difficulties persist, provide artificial respiration if required.
Toxicity Data
The oral LD50 (lethal dose for 50% of the population) is 250 mg/kg in dogs. The dermal LD50 is reported to be between 64 to 160 mg/kg in rats. For inhalation exposure, the LC50 (lethal concentration for 50% of the population) is greater than 5 mg/L over a 6-hour exposure period in rats.
Health Effects
Bronopol may react to produce nitrosamines, which are believed to be carcinogenic. It also releases formaldehyde, a known human carcinogen.
Adverse Effects
Skin Sensitizer – An agent that can induce an allergic reaction in the skin.
Exposure Routes
The substance can be absorbed into the body by inhalation of its aerosol, through the skin and by ingestion.
Carcinogen Classification
There is no indication of carcinogenicity, as the substance is not listed by IARC.
Antidote and Emergency Treatment
Advanced treatment involves considering orotracheal or nasotracheal intubation for airway control in patients who are unconscious, experiencing severe pulmonary edema, or in severe respiratory distress, with early intubation at the first sign of upper airway obstruction.
Positive-pressure ventilation techniques using a bag-valve mask may be beneficial, and drug therapy for pulmonary edema should be considered. Cardiac rhythm must be monitored, and arrhythmias treated as necessary. Begin IV administration of D5W at a minimal flow rate to keep the line open, and use 0.9% saline or lactated Ringer’s solution if hypovolemia is present.
For hypotension with signs of hypovolemia, administer fluids cautiously while watching for signs of fluid overload. Seizures should be treated with diazepam or lorazepam, and proparacaine hydrochloride can assist with eye irrigation when needed for irritating materials.
Properties of Bronopol
Chemical Identifiers
| EC Number | 200-143-0 |
| UNII | 6PU1E16C9W |
| InChIKey | LVDKZNITIUWNER-UHFFFAOYSA-N |
| SMILES | C(C(CO)(N+[O-])Br)O |
| IUPAC Name | 2-bromo-2-nitropropane-1,3-diol |
| InChI | InChI=1S/C3H6BrNO4/c4-3(1-6,2-7)5(8)9/h6-7H,1-2H2 |
Physical and Chemical Properties
Bronopol is chemically known as 2-bromo-2-nitropropane-1,3-diol, is characterized by its white crystalline form. It is highly flammable and can ignite easily, burning with intensity. Under conditions of significant shock, it has the potential to detonate. When subjected to heat, Bronopol undergoes decomposition, releasing hazardous gases. Additionally, it poses health risks as it can be absorbed through the skin, inhaled, or ingested, leading to toxic effects. Proper handling and storage are essential to mitigate these risks.
| Property | Value |
| LogP | -0.6 |
| Odor | Odorless |
| Density | Relative density (water = 1): 1.9 |
| Color/Form | White crystalline powder |
| Solubility | Greater than or equal to 100 mg/mL at 63°F |
| Flash Point | 167°C |
| Boiling Point | 305.1°F at 760 mmHg |
| Melting Point | 266 to 271°F |
| Decomposition | Decomposes on heating or burning produces toxic and corrosive fumes, including hydrogen bromide and nitrogen oxides. |
| Vapor Density | 1.2601e-05 mmHg at 68°F |
| Stability/Shelf Life | Slightly hygroscopic. Stable under normal storage conditions, but unstable in aluminum containers. |
| Other Experimental Properties | Stable at room temperature, high temperature, and in sunlight. |
Structural Properties
The structural properties of Bronopol indicate that it is a relatively simple compound with a molecular weight of about 200 g/mol. It has 9 atoms and is stable with no formal charge. The compound can form 2 rotatable bonds and has hydrogen bonding capabilities, with 2 hydrogen bond donors and 4 acceptors. The surface area that interacts with water is moderate. The compound is canonicalized, meaning it is in its most stable form. Overall, its structure suggests it is a small, moderately polar compound suitable for a range of chemical interactions.
| Property | Value |
| XLogP3 | -0.6 |
| Complexity | 107 |
| Exact Mass | 198.94802 g/mol |
| Formal Charge | 0 |
| Heavy Atom Count | 9 |
| Molecular Weight | 199.99 g/mol |
| Monoisotopic Mass | 198.94802 g/mol |
| Isotope Atom Count | 0 |
| Rotatable Bond Count | 2 |
| Compound Is Canonicalized | Yes |
| Hydrogen Bond Donor Count | 2 |
| Hydrogen Bond Acceptor Count | 4 |
| Covalently-Bonded Unit Count | 1 |
| Topological Polar Surface Area | 86.3 Ų |
| Defined Atom Stereocenter Count | 0 |
| Defined Bond Stereocenter Count | 0 |
| Undefined Atom Stereocenter Count | 0 |
| Undefined Bond Stereocenter Count | 0 |
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