Parabens: Environment tier II assessment

Preface

This assessment was carried out by staff of the National Industrial Chemicals Notification and Assessment Scheme (NICNAS) using the Inventory Multi-tiered Assessment and Prioritisation (IMAP) framework.

The IMAP framework addresses the human health and environmental impacts of previously unassessed industrial chemicals listed on the Australian Inventory of Chemical Substances (the Inventory).

The framework was developed with significant input from stakeholders and provides a more rapid, flexible and transparent approach for the assessment of chemicals listed on the Inventory.

Stage One of the implementation of this framework, which lasted four years from 1 July 2012, examined 3000 chemicals meeting characteristics identified by stakeholders as needing priority assessment. This included chemicals for which NICNAS already held exposure information, chemicals identified as a concern or for which regulatory action had been taken overseas, and chemicals detected in international studies analysing chemicals present in babies’ umbilical cord blood.

Stage Two of IMAP began in July 2016. We are continuing to assess chemicals on the Inventory, including chemicals identified as a concern for which action has been taken overseas and chemicals that can be rapidly identified and assessed by using Stage One information. We are also continuing to publish information for chemicals on the Inventory that pose a low risk to human health or the environment or both. This work provides efficiencies and enables us to identify higher risk chemicals requiring assessment.

The IMAP framework is a science and risk-based model designed to align the assessment effort with the human health and environmental impacts of chemicals. It has three tiers of assessment, with the assessment effort increasing with each tier. The Tier I assessment is a high throughput approach using tabulated electronic data. The Tier II assessment is an evaluation of risk on a substance-by-substance or chemical category-by-category basis. Tier III assessments are conducted to address specific concerns that could not be resolved during the Tier II assessment.

These assessments are carried out by staff employed by the Australian Government Department of Health and the Australian Government Department of the Environment and Energy. The human health and environment risk assessments are conducted and published separately, using information available at the time, and may be undertaken at different tiers.

This chemical or group of chemicals are being assessed at Tier II because the Tier I assessment indicated that it needed further investigation.

For more detail on this program please visit: www.nicnas.gov.au.

Disclaimer

NICNAS has made every effort to assure the quality of information available in this report. However, before relying on it for a specific purpose, users should obtain advice relevant to their particular circumstances.  This report has been prepared by NICNAS using a range of sources, including information from databases maintained by third parties, which include data supplied by industry.  NICNAS has not verified and cannot guarantee the correctness of all information obtained from those databases.  Reproduction or further distribution of this information may be subject to copyright protection. Use of this information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.  NICNAS does not take any responsibility whatsoever for any copyright or other infringements that may be caused by using this information.

Acronyms & Abbreviations

Grouping Rationale

This Tier II assessment considers the environmental risks associated with the industrial uses of a group of eighteen esters of para-hydroxybenzoic acid (pHBA). All eighteen chemicals, known as parabens, have industrial uses as antimicrobial preservatives.

Parabens are used as preservatives in a range of applications, including cosmetics, personal care and cleaning products, which are released into sewers as a normal part of their use in domestic and industrial situations. The use of parabens in these products has significant potential to result in environmental exposure through a common pathway involving releases of the chemicals in the treated effluents and biosolids produced by sewage treatment plants (STP).

The Tier I assessment of some chemicals in this group indicated potential for unreasonable risks to the environment from their emission to surface waters in treated effluent from STPs. Based on their similar structures and uses, the chemicals in this group are each expected to present generally similar environmental concerns for industrial uses in Australia.

The sodium and potassium cations present as counter ions in salts of this group are ubiquitous, naturally occurring inorganic species that are essential for many biological functions. These cations are not further considered in this assessment.

Chemical Identity

CAS RN

99-76-3

Chemical Name

Benzoic acid, 4-hydroxy-, methyl ester

Synonyms

methylparaben

Structural Formula

Chemical structure of Benzoic acid, 4-hydroxy-, methyl ester (CAS-RN 99-76-3)

Molecular Formula

C8H8O3

Molecular Weight (g/mol)

152.15

SMILES

C(=O)(c1ccc(O)cc1)OC

CAS RN

5026-62-0

Chemical Name

Benzoic acid, 4-hydroxy-, methyl ester, sodium salt

Synonyms

sodium methylparaben

Structural Formula

Chemical structure of Benzoic acid, 4-hydroxy-, methyl ester, sodium salt (CAS-RN 5026-62-0)

Molecular Formula

C8H7NaO3

Molecular Weight (g/mol)

174.13

SMILES

C(=O)(c1ccc([O-])cc1)OC.[Na+]

CAS RN

26112-07-2

Chemical Name

Benzoic acid, 4-hydroxy-, methyl ester, potassium salt

Synonyms

potassium methylparaben

Structural Formula

Chemical structure of Benzoic acid, 4-hydroxy-, methyl ester, potassium salt (CAS-RN 26112-07-2)

Molecular Formula

C8H7KO3

Molecular Weight (g/mol)

191.25

SMILES

C(=O)(c1ccc([O-])cc1)OC.[K+]

CAS RN

120-47-8

Chemical Name

Benzoic acid, 4-hydroxy-, ethyl ester

Synonyms

ethylparaben

Structural Formula

Chemical structure of Benzoic acid, 4-hydroxy-, ethyl ester (CAS-RN 120-47-8)

Molecular Formula

C9H10O3

Molecular Weight (g/mol)

166.17

SMILES

C(=O)(c1ccc(O)cc1)OCC

CAS RN

35285-68-8

Chemical Name

Benzoic acid, 4-hydroxy-, ethyl ester, sodium salt

Synonyms

sodium ethylparaben

Structural Formula

Chemical structure of Benzoic acid, 4-hydroxy-, ethyl ester, sodium salt (CAS-RN 35285-68-8)

Molecular Formula

C9H9NaO3

Molecular Weight (g/mol)

188.15

SMILES

C(=O)(c1ccc([O-])cc1)OCC.[Na+]

CAS RN

36457-19-9

Chemical Name

Benzoic acid, 4-hydroxy-, ethyl ester, potassium salt

Synonyms

potassium ethylparaben

Structural Formula

Chemical structure of Benzoic acid, 4-hydroxy-, ethyl ester, potassium salt (CAS-RN 36457-19-9)

Molecular Formula

C9H9KO3

Molecular Weight (g/mol)

204.26

SMILES

C(=O)(c1ccc([O-])cc1)OCC.[K+]

CAS RN

94-13-3

Chemical Name

Benzoic acid, 4-hydroxy-, propyl ester

Synonyms

propylparaben

Structural Formula

Chemical structure of Benzoic acid, 4-hydroxy-, propyl ester (CAS-RN 94-13-3)

Molecular Formula

C10H12O3

Molecular Weight (g/mol)

180.20

SMILES

C(=O)(c1ccc(O)cc1)OCCC

CAS RN

35285-69-9

Chemical Name

Benzoic acid, 4-hydroxy-, propyl ester, sodium salt

Synonyms

sodium propylparaben

Structural Formula

Chemical structure of Benzoic acid, 4-hydroxy-, propyl ester, sodium salt (CAS-RN 35285-69-9)

Molecular Formula

C10H11NaO3

Molecular Weight (g/mol)

202.18

SMILES

C(=O)(c1ccc([O-])cc1)OCCC.[Na+]

CAS RN

84930-16-5

Chemical Name

Benzoic acid, 4-hydroxy-, propyl ester, potassium salt

Synonyms

potassium propylparaben

Structural Formula

Chemical structure of Benzoic acid, 4-hydroxy-, propyl ester, potassium salt (CAS-RN 84930-16-5)

Molecular Formula

C10H11KO3

Molecular Weight (g/mol)

219.30

SMILES

C(=O)(c1ccc([O-])cc1)OCCC.[K+]

CAS RN

4191-73-5

Chemical Name

Benzoic acid, 4-hydroxy-, isopropyl ester

Synonyms

isopropylparaben

Structural Formula

Chemical structure of Benzoic acid, 4-hydroxy-, 1-methylethyl ester (CAS-RN 4191-73-5)

Molecular Formula

C10H12O3

Molecular Weight (g/mol)

180.20

SMILES

C(=O)(c1ccc(O)cc1)OC(C)C

CAS RN

94-26-8

Chemical Name

Benzoic acid, 4-hydroxy-, butyl ester

Synonyms

butylparaben

Structural Formula

Chemical structure of Benzoic acid, 4-hydroxy-, butyl ester (CAS-RN 94-26-8)

Molecular Formula

C11H14O3

Molecular Weight (g/mol)

194.23

SMILES

C(=O)(c1ccc(O)cc1)OCCCC

CAS RN

36457-20-2

Chemical Name

Benzoic acid, 4-hydroxy-, butyl ester, sodium salt

Synonyms

sodium butylparaben

Structural Formula

Chemical structure of Benzoic acid, 4-hydroxy-, butyl ester, sodium salt (CAS-RN 36457-20-2)

Molecular Formula

C11H13NaO3

Molecular Weight (g/mol)

217.22

SMILES

C(=O)(c1ccc([O-])cc1)OCCCC.[Na+]

CAS RN

4247-02-3

Chemical Name

Benzoic acid, 4-hydroxy-, isobutyl ester

Synonyms

isobutylparaben

Structural Formula

Chemical structure of Benzoic acid, 4-hydroxy-, 2-methylpropyl ester (CAS-RN 4247-02-3)

Molecular Formula

C11H14O3

Molecular Weight (g/mol)

194.23

SMILES

C(=O)(c1ccc(O)cc1)OCC(C)C

CAS RN

1085-12-7

Chemical Name

Benzoic acid, 4-hydroxy-, heptyl ester

Synonyms

heptylparaben

Structural Formula

Chemical structure of Benzoic acid, 4-hydroxy-, heptyl ester (CAS-RN 1085-12-7)

Molecular Formula

C14H20O3

Molecular Weight (g/mol)

236.31

SMILES

C(=O)(c1ccc(O)cc1)OCCCCCCC

CAS RN

1219-38-1

Chemical Name

Benzoic acid, 4-hydroxy-, octyl ester

Synonyms

octylparaben

Structural Formula

Chemical structure of Benzoic acid, 4-hydroxy-, octyl ester (CAS-RN 1219-38-1)

Molecular Formula

C15H22O3

Molecular Weight (g/mol)

250.34

SMILES

C(=O)(c1ccc(O)cc1)OCCCCCCCC

CAS RN

5153-25-3

Chemical Name

Benzoic acid, 4-hydroxy-, 2-ethylhexyl ester

Synonyms

ethylhexylparaben

isooctylparaben

Structural Formula

Chemical structure of Benzoic acid, 4-hydroxy-, 2-ethylhexyl ester (CAS-RN 5153-25-3)

Molecular Formula

C15H22O3

Molecular Weight (g/mol)

250.34

SMILES

C(=O)(c1ccc(O)cc1)OCC(CCCC)CC

CAS RN

2664-60-0

Chemical Name

Benzoic acid, 4-hydroxy-, dodecyl ester

Synonyms

laurylparaben

dodecylparaben

Structural Formula

Chemical structure of Benzoic acid, 4-hydroxy-, dodecyl ester (CAS-RN 2664-60-0)

Molecular Formula

306.45

Molecular Weight (g/mol)

C19H30O3

SMILES

C(=O)(c1ccc(O)cc1)OCCCCCCCCCCCC

CAS RN

94-18-8

Chemical Name

Benzoic acid, 4-hydroxy-, phenylmethyl ester

Synonyms

benzylparaben

Structural Formula

Chemical structure of Benzoic acid, 4-hydroxy-, phenylmethyl ester (CAS-RN 94-18-8)

Molecular Formula

C14H12O3

Molecular Weight (g/mol)

228.25

SMILES

C(=O)(c1ccc(O)cc1)OCc1ccccc1

Physical and Chemical Properties

The physical and chemical property data for representative members of this group were retrieved from the databases included in the OECD QSAR Toolbox or calculated using EPI Suite (LMC, 2013, US EPA, 2008). The range of properties for the selected chemicals are expected to encompass the physical and chemical properties of the other neutral organic chemicals in this group:

Chemical

methylparaben

propylparaben

laurylparaben

benzylparaben

Physical Form

solid

solid

solid

solid

Melting Point

131°C (exp.)

97°C (exp.)

142°C (calc.)

111°C (exp.)

Boiling Point

275°C (exp.)

301°C (exp.)

398°C (calc.)

355°C (calc.)

Vapour Pressure

5.5 × 10-5 Pa (exp.)

8.2 × 10-4 Pa (exp.)

1.6 × 10-5 Pa (calc.)

5.0 × 10-4 Pa (calc.)

Water Solubility

2500 mg/L (exp.)

500 mg/L (exp.)

0.02 mg/L (calc.)

23.4 mg/L (calc.)

Ionisable in the Environment?

yes

yes

yes

yes

log Kow

1.96 (exp.)

3.04 (exp.)

7.40 (calc.)

3.56 (exp.)

With the exception of benzylparaben, the chemicals in this group differ only in the length and branching of their respective ester group alkyl chains. Based on experimental and calculated values for key chemical properties, the water solubility decreases and log Kow (lipophilicity) increases as the carbon chain length of the ester alkyl group increases.

The value of the acid dissociation constant (pKa) is relatively unaffected by the structural variations in the alkyl chain, with the calculated and measured pKa values for the chemicals in this group ranging from 7.9 to 8.5. The branched and linear isomers of parabens with the same alkyl chain length (e.g. butyl- and isobutylparaben) have similar physicochemical characteristics.

Import, Manufacture and Use

Australia

All parabens in this group with an alkyl chain length of 1-4 carbons (the short-chain parabens: methyl-, ethyl-, propyl- and butylparaben including their salts and isomers) have been reported to be used as antimicrobial preservatives in cosmetics in Australia. In addition, propylparaben and methylparaben are reported to be used in surface coatings (NICNAS, 2016).

Parabens may also be used in food and pharmaceuticals in Australia (NICNAS, 2016). The environmental risk of use in these applications is beyond the scope of this assessment.

International

Parabens are widely used antimicrobial ingredients that are present in cosmetics and personal care products, as well as cleaning products and paints. Methylparaben and propylparaben are the most common parabens, and are often used in combination to increase efficacy (Madsen, et al., 2001, Nordic Council of Ministers, 2015).

Sodium methylparaben, ethylparaben and propylparaben are currently registered for use in the European Union (EU) at 100 to 1000 tonnes per annum each, while methylparaben is registered for use at 1000 to 10 000 tonnes per annum. These chemicals are reported to be used in cosmetics, personal care products, fragrances, adhesives and sealants. Benzylparaben is registered for use in the EU at 1 to 10 tonnes per annum, with reported uses in coatings and in manufacturing (ECHA, 2015b).

A study conducted in the United States of America (USA) found parabens, including methyl-, ethyl-, propyl-, butyl-, benzyl- and heptylparaben, to be present in personal care products. Methylparaben was the most frequently identified, being found in 64% of leave-on personal care products, 60% of baby care products and 39% of rinse-off personal care products. Similar use frequency was found for propylparaben. Ethylparaben and butylparaben were found in 10-35% of products, while benzylparaben and heptylparaben were found in 0-15% of products. Benzylparaben and heptylparaben were found at much lower concentrations than the short-chain parabens (Guo and Kannan, 2013).

Isobutylparaben, isopropylparaben and benzylparaben are listed on Annex II of the EC Regulation 1223/2009 (the Cosmetics Directive), prohibiting their use in cosmetic products marketed in the EU. The Scientific Committee on Consumer Safety was unable to evaluate the risks posed by these chemicals to human health due to a lack of industry-submitted information (European Commission, 2014). The remaining parabens are listed on Annex V, restricting their use in cosmetic formulations to 0.4% w/w for a single paraben and 0.8% w/w for a combination of parabens (European Commission, 2009, 2014 ).

In Japan, a maximum total paraben concentration of 1% w/w is allowed in cosmetic products (Terasaki, et al., 2015).

The Association of Southeast Asian Nations (ASEAN) has prohibited the use of isopropyl-, isobutyl‑, and benzylparaben as preservatives in cosmetics (ACA, 2016).

Environmental Regulatory Status

Australia

The use of the chemicals in this group is not subject to any specific national environmental regulations.

United Nations

No chemicals in this group are currently identified as a Persistent Organic Pollutant (UNEP, 2001), ozone depleting substance (UNEP, 1987), or hazardous substance for the purpose of international trade (UNEP & FAO, 1998).

OECD

No chemicals in this group have been sponsored for assessment under the Cooperative Chemicals Assessment Programme (OECD, 2015).

Canada

Isooctylparaben and benzylparaben were screened during the Categorization of the Domestic Substances List (DSL) and found to be Not Persistent (Not P), Not Bioaccumulative (Not B) and Inherently Toxic to the Environment (iTE) (Environment Canada, 2013).

Methyl-, ethyl-, and propylparaben and their sodium salts, and butyl-, isobutyl-, and isopropylparaben were screened during the Categorization of the DSL and found to be Not Persistent (Not P), Not Bioaccumulative (Not B) and Not Inherently Toxic to the Environment (Not iTE) (Environment Canada, 2013).

The remaining members of this group were not screened during the Categorization of the DSL.

European Union

None of the chemicals in this group are listed on the Candidate List for Eventual Inclusion in Annex XIV, Annex XIV (authorisation) or Annex XVII (restriction) of the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) legislation. Therefore, the chemicals in this group are not subject to authorisation or restriction, and are not currently identified by the European Union as Substances of Very High Concern for the environment (SVHC) (ECHA, 2013, 2014, 2017).

Methyl-, ethyl-, propyl-, isobutyl-, and benzylparaben and the sodium salts of methyl-, ethyl- and propylparaben are registered under REACH (ECHA, 2015a). The remaining chemicals in this group are pre-registered under REACH.

Methyl-, ethyl- and propylparaben are currently listed on the Community Rolling Action Plan (CoRAP), indicating that these chemicals are considered as priorities for evaluation by a Member State, due to concerns regarding their high volumes of use and potential endocrine activity (ECHA, 2016a). In addition, methylparaben and propylparaben are listed on the Public Activities Coordination Tool (PACT) as appropriate for informal hazard assessment and/or risk management option analysis under the SVHC Roadmap (ECHA, 2016b) due to their possible endocrine activity.

United States of America

The chemicals in this group do not belong to any of the chemical classes covered by Existing Chemical Action Plans and have not been selected for action plan development (US EPA, 2016).

Environmental Exposure

Based on available domestic and international use data, parabens from this group are expected to be found in a range of household and commercial products available for use in Australia.

Chemicals used in cosmetics and cleaning products are typically released to sewers as a normal part of their use in domestic and industrial applications. Studies on the fate of parabens in STPs have indicated that removal from influent is above 90% (Haman, et al., 2015), with degradation and adsorption to sludge being major mechanisms of removal. Parabens may be released to the environment in treated effluent, while those removed by adsorption to sludge may be applied to land as biosolids. Hence, emissions of parabens to both environmental surface waters and soils are considered as part of this assessment.

Environmental Fate

Dissolution, Partitioning and Speciation

The chemicals in this group are expected to primarily remain in their compartment of release, with movement from the water to the sediment compartment increasing with lipophilicity.

The salts in this group dissociate in water to their respective paraben mono-anion and inorganic cation. The organic anion and neutral protonated form of each paraben ester are in pH dependent equilibrium and both occur under environmental conditions.

Parabens are expected to be slightly to readily soluble in water with low to moderate volatility (LMC, 2013, US EPA, 2008). Estimated Henry’s Law constants for the group indicate very slight volatility from water and moist soil (US EPA, 2008). The mobility of this group of chemicals in soil is expected to decrease with increasing lipophilicity, which is proportional to the soil adsorption coefficient (KOC). While the less lipophilic chemicals such as methylparaben (predicted log KOC = 1.9), are expected to have high mobility in soil, the more lipophilic chemicals such as laurylparaben (predicted log KOC = 4.8), are expected to be immobile (US EPA, 2008).

Calculations with a standard multimedia partitioning (fugacity) model assuming equal and continuous distributions to air, water and soil compartments (Level III approach) predict that, under steady state conditions, the chemicals in this group will mainly partition to the soil compartment (approximately 70–80%), with moderate partitioning to the water compartment (approximately 20%) and, for more lipophilic substances, the sediment compartment (up to approximately 15%) (US EPA, 2008). All chemicals in this group are expected to primarily remain in the soil compartment if released solely to soil (> 95%) (US EPA, 2008). However, with sole release to the water compartment, various partitioning patterns are predicted. Laurylparaben, being more lipophilic, is expected to partition roughly equally between the water and sediment compartments. In contrast, methylparaben is expected to remain in the water compartment (US EPA, 2008).

Degradation

The chemicals in this group are expected to be both biodegradable in the environment, and susceptible to abiotic degradation processes. Chlorinated paraben transformation products are also expected to be biodegradable, though with longer half-lives than the parent paraben.

Biodegradation of the more commonly used parabens has been well studied. Methylparaben, ethylparaben and propylparaben have all been found to undergo 89–92% biodegradation in 28 days in studies conducted in accordance with OECD Test Guideline (TG) 301F (ECHA, 2015b, Madsen, et al., 2001). Another study investigated the primary biodegradation of parabens in water with an activated sludge inoculant, according to ISO 7827 (González-Mariño, et al., 2011). The short-chain parabens had primary degradation half-lives of 1.8–3.7 days, with 99% primary degradation observed at between 2.1 and 4.5 days.

A biodegradation study conducted with river water as the inoculant found that benzylparaben had a half-life of 10–19 hours depending on temperature and origin of the river water inoculant (Yamamoto, et al., 2007b). In addition, biodegradation calculations for benzylparaben gave an ultimate biodegradation half-life of 14.1 days (LMC, 2011).

No biodegradation data were identified for the parabens with alkyl chain length of 7–12 carbons (the long-chain parabens; heptyl-, octyl-, isooctyl- and laurylparaben). Calculated biodegradation rates for the long-chain parabens gave ultimate biodegradation half-lives of 9.5–10.4 days for the linear parabens and 20.1 days for the branched isooctylparaben.

Abiotic processes may also represent significant degradation pathways for the chemicals in this group. Yamamoto et al. (2007b) reported a photolysis half life of less than one day for benzylparaben in water under natural light, with photolysis half lives for butylparaben and isobutylparaben ranging from 14.6 to 24.2 days.

Parabens are stable in acidic conditions, but can undergo hydrolysis above pH 7. The methylparaben hydrolysis half-life at pH 8 is calculated to be 1260 days, and increases with longer ester alkyl chains. Hence, abiotic hydrolysis is not expected to be a significant degradation pathway for parabens (Haman, et al., 2015, US EPA, 2008). Biotic or abiotic hydrolysis of the ester bond produces pHBA as a degradation product common to all parabens (Valkova, et al., 2001). pHBA is a chemical that has been assessed at Tier I level under the IMAP Framework and found to be of low concern to the environment (NICNAS, 2017).

Parabens readily undergo halogenation on the aromatic ring carbons ortho to the hydroxyl group to form several mono- and di-halogenated species (Canosa, et al., 2006). These chemical derivatives can be formed in chlorinated waters such as drinking water, and during chlorine treatment in STPs. They show slower biodegradation than the parent compounds; in a biodegradation study according to ISO 7827 using activated sludge as the inoculant, dichloromethylparaben (3,5-dichloro-4-hydroxybenzoic acid methyl ester, CAS RN 3337-59-5) had a half-life of 8.7 days, compared to 1.8 days for the parent chemical methylparaben (González-Mariño, et al., 2011). In this study, 99% primary degradation of dichloromethylparaben was achieved after 16 days.

Bioaccumulation

The short-chain parabens in this group and benzylparaben are not expected to bioaccumulate, while the long-chain parabens in this group have the potential to bioaccumulate.

Low octanol-water partition coefficient (KOW) values for the short-chain parabens and benzylparaben do not exceed the domestic categorisation threshold for bioaccumulation hazards in aquatic organisms (log KOW ≤ 4.2). This indicates limited bioaccumulation potential for these chemicals (LMC, 2013, US EPA, 2008 ).

There is evidence for rapid metabolism of short-chain parabens in fish; a 10-day feeding study showed that less than 1% of total ingested propylparaben was found in rainbow trout liver and muscle tissue after doses of 1830 mg kg-1 every second day (Bjerregaard, et al., 2003). Half-lives of 8.6 hours in liver and 1.5 hours in muscle tissue were derived. A similar study showed less than 1% of total butylparaben ingested at 51 mg kg-1 every second day over 12 days remained in rainbow trout liver tissue at the end of the experiment (Alslev, et al., 2005).

The long-chain parabens have measured or calculated KOW values which exceed the domestic categorisation threshold for bioaccumulation hazards in aquatic organisms (log KOW > 4.2) (LMC, 2013, US EPA, 2008). High octanol-water partition coefficients can indicate high bioaccumulation potential, as the chemical may preferentially partition to lipid-rich tissues. This potential may be reduced by possible metabolism in biota, as seen for propyl- and butylparaben. Bioconcentration modelling for these compounds incorporating estimated rates of biotransformation in fish gave BCF values of 76–1598 L/kg for heptyl-, octyl- and isooctylparaben, and 2148 L/kg for laurylparaben (US EPA, 2008).

A series of studies of parabens and their metabolites in biota found methylparaben and pHBA at high concentrations in many marine organisms (Xue, et al., 2015, Xue and Kannan, 2016, Xue, et al., 2017). A trophic magnification factor of 1.83 was calculated for methylparaben in one food web. It was noted that methylparaben could be formed from pHBA through biotransformation by gut microflora. The trophic magnification of methylparaben would, therefore, be partially reliant on the availability of a high concentration of pHBA, which can arise from ester hydrolysis of any paraben, or from natural sources. The highest methylparaben concentration was found in the liver of a bottlenose dolphin, at 865 ng/g wet weight.

Transport

The chemicals in this group have low potential for long-range transport.

The rapid environmental degradation of the chemicals in this group indicates that they will be unlikely to undergo long-range transport. Further, the parabens in this group are expected to have only very slight volatility from water and moist soil (US EPA, 2008), resulting in limited partitioning to the air compartment where long-range transport typically occurs.

Predicted Environmental Concentration (PEC)

Predicted environmental concentrations were estimated for the chemicals in this group based on available international and domestic monitoring data, as well as calculated data.

In the absence of comprehensive reported Australian environmental monitoring data, standard exposure modelling for the release of chemicals to surface waters in STP effluents (Struijs, 1996) was used to calculate riverine environmental concentrations, assuming annual introduction volumes of 100 tonnes (NICNAS, 2013). The calculated riverine PECs from this analysis are 7.88 micrograms per litre (µg/L) for methyl- and ethylparaben, 7.27 µg/L for propylparaben, 6.66 µg/L for butyl- and benzylparaben, and 4.85 µg/L for heptyl-, octyl- and isooctylparaben.

These calculated values are reasonably consistent with available domestic monitoring data for the short-chain parabens. A study focusing on the concentrations of the short-chain parabens in urban water and stormwater drainage systems in the Sydney metropolitan area took 72 water samples from a variety of sources across different land use areas (Evans, et al., 2016). Methylparaben was detected at an average concentration of 5.41 µg/L and a highest observed concentration of 13.78 µg/L. Ethylparaben was detected at an average and highest concentration of 13.86 and 305.55 µg/L respectively, propylparaben at an average and highest concentration of 2.97 and 8.29 µg/L respectively, and butylparaben at an average and highest concentration of 4.36 and 8.47 µg/L respectively. The study also sampled STP effluent, finding highest concentrations of methyl-, ethyl-, propyl- and butylparaben to be 12.28, 4.95, 3.15 and 4.82 µg/L, respectively.

The highest observed concentration of each paraben were from diverse water sources, covering both riverwater and stormwater samples from both industrial and residential land use areas. The sample containing ethylparaben at 305.55 µg/L was taken from the Duck River, downstream from an industrial area including a waste transfer station.

Based on these domestic monitoring data, and for the purposes of this assessment, the PECs for methyl-, ethyl-, propyl- and butylparaben are determined to be 13.78, 305.55, 8.29 and 8.47 µg/L, respectively.

It is noted that these measured concentrations for parabens are somewhat higher than results from international monitoring studies (Evans, et al., 2016). Methyl- and propylparaben are the most commonly detected parabens, and at higher concentrations than other parabens due to their combined use in cosmetics (Guo and Kannan, 2013). In effluent from a Spanish STP, methyl- and propylparaben were found at maximum concentrations of 50 and 21 nanograms per litre (ng/L) respectively, with lower maximum concentrations of ethyl- and butylparaben (González-Mariño, et al., 2011). Two studies on parabens in Japanese rivers found methyl- and propylparaben at maximum concentrations of 525 and 181 ng/L respectively (Kimura, et al., 2014), and 676 and 207 ng/L respectively (Yamamoto, et al., 2011). These maximum concentrations are all significantly lower than the mean values of parabens measured in Sydney surface waters and Sydney STP effluent (Evans, et al., 2016).

The long-chain parabens are very rarely detected in international monitoring studies, and at much lower concentrations than the short-chain parabens. Heptyl- and octylparaben were detected in urban surface water samples in Beijing at maximum concentrations of 2.94 and 4.89 ng/L respectively (Li, et al., 2016). In the same study, methylparaben was detected at a maximum concentration of 920 ng/L. Heptyl- and benzylparaben were found in influent waters of a STP in the Albany area in New York at maximum concentrations of 0.31 and 0.27 ng/L respectively (Wang and Kannan, 2016), indicating low emissions to waste waters. Benzylparaben was found at a maximum concentration of 3.93 ng/L in urban surface waters in Beijing, and two further studies concluded that benzylparaben was present below the limit of detection in STP effluent samples (González-Mariño, et al., 2011, Li, et al., 2015, Li, et al., 2016).

It would not be appropriate to predict the Australian environmental concentrations of heptyl-, octyl- or benzylparaben based on these international monitoring data, given the disparity between the measured domestic and international concentrations of the short-chain parabens. Therefore, the PECs for heptyl-, octyl- and isooctylparaben are taken to be 4.85 µg/L, and 6.66 µg/L for benzylparaben, based on calculations using the default introduction volume and the SimpleTreat model.

Chlorinated transformation products of parabens have been detected in wastewater treatment plant waters. At an STP in Beijing, 3,5-dichloromethylparaben and 3,5-dichloroethylparaben (3,5-dichloro-4-hydroxy benzoic acid ethyl ester, CAS RN 17302‑82‑8) were detected in effluent water after secondary treatment at mean concentrations of 13.6 and 19.8 ng/L respectively. These concentrations were higher than the effluent concentrations of their respective non-chlorinated parent parabens (Li, et al., 2015). In a second study, the average total chlorinated paraben concentration in river water was found to be 50.1 ng/L, compared to the average total paraben concentration of 44.3 ng/L (Li, et al., 2016). One study investigated chlorinated parabens in river water in Shizuoka City, Japan, as combined concentrations from suspended solid and dissolved phases (Terasaki, et al., 2012). Dichloromethylparaben was found in one sample at 6.1 ng/L, while dichloropropylparaben (3,5-dichloro-4-hydroxy benzoic acid propyl ester, CAS RN 101003-80-9) was found at up to 28 ng/L.

Environmental Effects

Effects on Aquatic Life

The chemicals in this group are slightly to highly toxic in aquatic organisms.

Acute toxicity

The following measured median lethal concentration (LC50) and median effective concentration (EC50) values for model organisms across three trophic levels for methylparaben (MeP), ethylparaben (EtP), propylparaben (PrP), butylparaben (BuP), benzylparaben (BzP), heptylparaben (HeP), and octylparaben (OcP) were reported (Dobbins, et al., 2009, ECHA, 2016c, Madsen, et al., 2001, Yamamoto, et al., 2007a, 2011), or calculated (US EPA, 2008).

Calculated data for the long-chain parabens indicate higher toxicity than short-chain parabens. This trend is consistent with previous studies, which demonstrated that the toxicity of parabens is proportional to their lipophilicity (Yamamoto, et al., 2011). This indicates that parabens’ acute toxicity is likely to be through non-specific disruption of cell membrane function (Terasaki, et al., 2009b). Calculated and measured toxicity values for the short-chain parabens were fairly consistent, therefore the calculated ecotoxicity endpoints for the long-chain parabens presented in the table below are expected to be reliable. Reliable values for acute ecotoxicity endpoints for laurylparaben cannot be calculated.

Data for the branched isomers in this group have not been presented. However, acute ecotoxicity endpoint values for isopropylparaben and isobutylparaben have been published (Dobbins, et al., 2009, Yamamoto, et al., 2007a, 2011). The calculated acute ecotoxicity of octyl- and isooctylparaben are very similar. These values indicate that the acute toxicity of the branched isomers is expected to be similar to or less than that of the straight chain isomers:

Taxon

Endpoint

Method

Fish

MeP: 96 h LC50 = 60 mg/L
EtP: 96 h LC50 = 14 mg/L
PrP: 96 h LC50 = 4.9 mg/L
BuP: 96 h LC50 = 2.9 mg/L
BzP: 96 h LC50 = 0.73 mg/L

Experimental
Oryzias latipes (Japanese medaka)
OECD TG 203

 

HeP: 96 h LC50 = 0.238 mg/L
OcP: 96 h LC50 = 0.107 mg/L

Calculated
ECOSAR

Invertebrate

MeP: 48 h EC50 = 11.2 mg/L

Experimental
Daphnia magna
ISO 6341

 

EtP: 48 h EC50 = 7.4 mg/L
PrP: 48 h EC50 = 2.0 mg/L
BuP: 48 h EC50 = 1.9 mg/L
BzP: 48 h EC50 = 2.1 mg/L

Experimental
Daphnia magna
OECD TG 202

 

HeP: 48 h EC50 = 0.265 mg/L
OcP: 48 h EC50 = 0.148 mg/L

Calculated
ECOSAR

Algae

MeP: 72 h EC50 = 30 mg/L
PrP: 72 h EC50 = 7.6 mg/L
BuP: 72 h EC50 = 9.5 mg/L
BzP: 72 h EC50 = 1.2 mg/L

Experimental
Pseudokirchneriella subcapacita (green algae)
OECD TG 201

 

EtP: 72 h EC50 = 18 mg/L

Experimental
Pseudokirchneriella subcapacita
(green algae)
ISO 8692

 

HeP: 72 h EC50 = 0.917 mg/L
OcP: 72 h EC50 = 0.488 mg/L

Calculated
ECOSAR

A study investigated the comparative acute invertebrate toxicities of parabens and their chlorinated transformation products according to OECD TG 202 (Terasaki, et al., 2009b ). The dichlorinated transformation products of methyl-, ethyl- and propylparaben all showed increased acute toxicity compared to their parent parabens.

Chlorination increases the acute toxicity of the parabens with comparative EC50 values of 62 mg/L for methylparaben and 16 mg/L for dichloromethylparaben, 32 mg/L for ethylparaben and 13 mg/L for dichloroethylparaben, and 23 mg/L for propylparaben and 8.3 mg/L for dichloropropylparaben. This trend is consistent with the trend of increasing toxicity with increased lipophilicity of these chemicals, as the chlorinated parabens are more lipophilic than their parent paraben. These increases in acute toxicity may be a cause for concern when considered in the context of the increased persistence of the chlorinated parabens.

Chronic toxicity

The following no observed effect concentration (NOEC) and lowest observed effect concentration (LOEC) values for model organisms across three trophic levels for methylparaben, ethylparaben, propylparaben, butylparaben, and benzylparaben were reported (Dobbins, et al., 2009, ECHA, 2016c, Terasaki, et al., 2015, Yamamoto, et al., 2007a, 2011):

Taxon

Endpoint

Method

Fish

MeP: 7 d LOEC = 25 mg/L
EtP: 7 d LOEC = 17 mg/L
PrP 7 d LOEC = 2.5 mg/L
BuP: 7 d LOEC = 1.0 mg/L
BzP: 7 d LOEC = 1.7 mg/L

Experimental
Pimephalas promelas
US EPA Method 1000.0
7d Larval survival and growth test

Invertebrate

MeP: 21 d NOEC = 0.2 mg/L

Experimental
Daphnia magna
OECD TG 211

 

EtP: 10 d LOEC = 2.3 mg/L
PrP: 10 d LOEC = 0.4 mg/L
BuP: 10 d LOEC = 0.2 mg/L

Experimental
Daphnia magna
US EPA SERAS SOP 2028
10d Chronic toxicity test

 

BzP: 7 d NOEC < 0.04 mg/L

Experimental
Ceriodaphnia dubia
EPS 1/RM/21
Reproduction and survival

Algae

MeP: 72 h NOEC = 12 mg/L
EtP: 72 h NOEC = 2.1 mg/L
PrP: 72 h NOEC = 2.1 mg/L
BuP: 72 h NOEC = 0.8 mg/L
BzP: 72 h NOEC = 0.52 mg/L

Experimental
Pseudokirchneriella subcapacita
OECD TG 201

A study investigated the comparative chronic toxicity of parabens and their chlorinated transformation products in the invertebrate C. dubia (Terasaki, et al., 2015). In contrast with the comparative study of acute toxicity, the chronic toxicity of chlorinated parabens were lower than that of their parent compounds.

Endocrine Activity

Parabens are considered to have (o)estrogenic activity, though at much lower potency than naturally produced (o)estrogens (NICNAS, 2016).

The (o)estrogenic effect of parabens in fish has been investigated in a number of studies. (O)estrogenic activity in fish can be measured by blood vitellogenin levels, a known biomarker for exposure to environmental (o)estrogens (Pedersen, et al., 2000). Propyl-, butyl- and benzylparaben have all been shown to increase the average blood vitellogenin concentration in studies conducted with rainbow trout or medaka, but at concentrations well above what is expected to be found in the environment (Alslev, et al., 2005, Bjerregaard, et al., 2003, Pedersen, et al., 2000, Yamamoto, et al., 2007a).

The (o)estrogenic effect of chlorinated paraben transformation products was investigated in a yeast assay incorporating the medaka estrogen receptor gene (Terasaki, et al., 2009a). Chlorinated parabens were found to generally have lower ability to activate the receptor than their parent parabens.

Effects on Sediment-dwelling Life

There are insufficient data available to evaluate the effects of these chemicals on sediment-dwelling organisms.

Effects on Terrestrial Life

The majority of toxicity testing on terrestrial organisms has been conducted on model organisms to evaluate the toxicity of parabens in humans. Further information on these studies can be found in the IMAP Tier II Human Health Assessment for Parabens (NICNAS, 2016).

Predicted No-Effect Concentration (PNEC)

A PNEC was not calculated for laurylparaben, as the chemical is predicted to have no effects at saturation. For all other chemicals in this group, the lowest calculated PNEC using the range of available ecotoxicity endpoint values and the appropriate assessment factor was used.

An assessment factor of 500 was used for heptylparaben, isooctylparaben and octylparaben. For these chemicals, predicted acute ecotoxicity endpoint values were used to calculate the PNEC. Normally, this would suggest the use of an assessment factor of 1000 (EPHC, 2009). However, this was able to be reduced in this assessment due to the high confidence associated with the structure-activity relationship (SAR) model utilised. The resulting PNEC values for these chemicals are less than 0.5 µg/L.

An assessment factor of 10 was used for methylparaben. A range of acute and chronic toxicity data are available for this chemical across three trophic levels. A chronic toxicity endpoint was used to derive the most conservative PNEC of 20 µg/L.

An assessment factor of 100 was used for ethyl-, propyl-, and butylparaben. A range of acute and chronic toxicity data are available for these chemicals across three trophic levels. Acute toxicity endpoints were selected, giving a range of PNECs from 19 to 74 µg/L.

An assessment factor of 50 was used for benzylparaben. A range of acute and chronic toxicity data are available for this chemical across three trophic levels. It was considered appropriate to use a more conservative assessment factor as the chronic toxicity endpoint selected was the lowest concentration used in the study (Terasaki, et al., 2015), and still elicited a significant effect on the test organism compared to the control. A PNEC of 0.8 µg/L was derived for this chemical.

Categorisation of Environmental Hazard

The categorisation of the environmental hazards of the chemicals in this group according to domestic environmental hazard thresholds is presented below (EPHC, 2009, NICNAS, 2013):

Persistence

Not Persistent (Not P). Based on the available measured and calculated data indicating rapid biodegradation and moderate to very rapid photo-transformation, the chemicals in this group are categorised as Not Persistent.

Bioaccumulation

Laurylparaben

Bioaccumulative (B). Based on log KOW values greater than 4.2 and a calculated mitigated BCF value > 2000 L/kg, laurylparaben is categorised as Bioaccumulative.

Heptylparaben, octylparaben, and isooctylparaben

Not Bioaccumulative (Not B). While the measured or calculated log KOW values are greater than 4.2, calculated mitigated BCF values are < 2000 L/kg for these chemicals, and there is evidence of rapid metabolism for the homologous short-chain parabens.

All remaining chemicals

Not Bioaccumulative (Not B). Based on log KOW values less than 4.2, and evidence of rapid metabolism, all remaining chemicals in this group are categorised as Not Bioaccumulative.

Toxicity

Heptylparaben, octylparaben, isooctylparaben and benzylparaben

Toxic (T). Based on measured or predicted acute toxicity values less than 1 mg/L, heptylparaben, octylparaben, isooctylparaben and benzylparaben are categorised as Toxic.

All remaining chemicals

Not Toxic (Not T). Based on measured acute toxicity endpoint values greater than 1 mg/L, and chronic toxicity endpoint values greater than 0.1 mg/L, all remaining chemicals in this group are categorised as Not Toxic.

Summary

Benzoic acid, 4-hydroxy-, dodecyl ester is categorised as:

  • Not P
  • B
  • Not T

Benzoic acid, 4-hydroxy-, heptyl ester; benzoic acid, 4-hydroxy-, octyl ester; benzoic acid, 4-hydroxy-, 2-isooctyl ester; and benzoic acid, 4-hydroxy-, phenylmethyl ester is categorised as:

  • Not P
  • Not B
  • T

All remaining chemicals in this group are categorised as:

  • Not P
  • Not B
  • Not T

Risk Characterisation

Based on the PEC and PNEC values determined above, Risk Quotients (RQ = PEC ÷ PNEC) for release into rivers were calculated for the chemicals in this group. Indicative RQ values for select members of this group are presented below:

Chemical

PEC (µg/L)

PNEC (µg/L)

RQ

methylparaben

13.78

20

0.69

ethylparaben

305.55

74

4.13

propylparaben

8.29

20

0.41

butylparaben

8.47

19

0.45

benzylparaben

6.66

0.8

8.33

heptylparaben

4.85

0.476

10.2

octylparaben

4.85

0.214

22.7

The RQ values for methyl-, propyl-, butylparaben, and their salts and branched isomers are below 1. This indicates that environmental concentrations are unlikely to exceed levels which cause ecotoxic effects in exposed organisms. Therefore, these chemicals are considered to be of low environmental concern.

An RQ greater than 1 indicates that the chemical may pose an unreasonable risk to the environment, as environmental concentrations may exceed levels that cause harmful effects. The RQ value for ethylparaben is 4.13. This RQ value is based on a very high measurement of ethylparaben in Sydney waters receiving runoff from an industrial area, which may not be representative of dispersive release of ethylparaben to Australian surface waters. If the average concentration of ethylparaben in Sydney waters is used, the RQ decreases to 0.19. Therefore, this chemical is considered to be of low environmental concern.

The RQ value for benzylparaben is 8.33. Benzylparaben has both the highest measured toxicity of the chemicals in this group and the highest (o)estrogenic activity in fish. However, evidence suggests that benzylparaben is a low volume chemical internationally, and that there is low potential for dispersive release based on its registered international uses in surface coatings and in manufacturing, and the prohibition of its use in cosmetic products in the EU.

The RQ values for heptylparaben, isooctylparaben and octylparaben ranged from 10.19 to 22.66. There is a high degree of uncertainty surrounding the PEC values calculated for these chemicals, as there is limited international information on their use volume or environmental concentration. These chemicals are also generally absent from consumer product ingredient databases. Based on low or unreported international use volumes and low potential for dispersive release, these RQ values are likely to overestimate the risk to surface waters in Australia from these long-chain parabens.

An RQ was not calculated for laurylparaben, as a PNEC was unable to be calculated for this chemical. As it has no toxic effects at saturation concentration, this chemical is expected to be of low environmental concern.

Ethyl-, propyl-, butyl- and benzylparaben have demonstrated (o)estrogenic activity in fish. While the level of activity is low, there may be potential for these chemicals to contribute to the total environmental xenoestrogenic load.

Chlorinated paraben transformation products have been detected in STP effluent at concentrations equivalent to their paraben parent compound. Insufficient information is available to fully characterise the risks posed by these transformation products. These transformation products degrade more slowly than the parent parabens, but also display lower chronic toxicity and reduced (o)estrogenic activity.

Insufficient information is available to characterise the risks posed by the release of the chemicals in this group to the sediment and soil compartments.

Key Findings

Parabens are widely used antimicrobial preservatives. Available data indicate industrial uses of some chemicals in this group in Australia in cosmetics and surface coatings.

The short chain parabens are readily biodegradable, have low bioaccumulation potential, and have moderate acute aquatic toxicity. They can be released to the environment through their industrial uses as preservatives in cosmetics and other consumer products. With the exception of ethylparaben, the estimated concentrations of each of these chemicals in river water are less than the respective PNECs calculated for each of these chemicals. Ethylparaben may have point source releases that pose a hazard to localised water systems, but dispersive release of this chemical to Australian surface waters is not expected to be of concern.

Benzylparaben and the long-chain parabens are likely to degrade rapidly in the environment and have high aquatic toxicity. These chemicals appear to have negligible use in cosmetics and consumer products; therefore, dispersive release to the environment is unlikely. Further assessment may be required if information becomes available to indicate that these chemicals have a use pattern that would result in release to the environment, or if measured environmental concentrations exceed the level of concern.

In addition to the characteristics considered in this assessment, available information suggests presence of chlorinated parabens at significant environmental concentrations. Further, it is unclear if the (o)estrogenic activity of parabens significantly contributes to cumulative environmental loads of xenoestrogens. These complexities have not been considered in-depth in this assessment.

The chemicals in this group are not PBT substances according to domestic environmental hazard criteria.

Recommendations

No further assessment is currently required.

Environmental Hazard Classification

In addition to the categorisation of environmental hazards according to domestic environmental thresholds presented above, the classification of the environmental hazards of the chemicals in this group according to the third edition of the United Nations’ Globally Harmonised System of Classification and Labelling of Chemicals (GHS) is presented below (UNECE, 2009).

Benzoic acid, 4-hydroxy-, dodecyl ester:

Hazard

GHS Classification (Code)

Hazard Statement

Acute Aquatic

-

Not classified

Chronic Aquatic

-

Not classified

Benzoic acid, 4-hydroxy-, methyl ester; benzoic acid, 4-hydroxy-, methyl ester, sodium salt; and benzoic acid, 4-hydroxy-, methyl ester, potassium salt:

Hazard

GHS Classification (Code)

Hazard Statement

Acute Aquatic

Category 3 (H402)

Harmful to aquatic life

Chronic Aquatic

Category 3 (H412)

Harmful to aquatic life with long lasting effects.

Benzoic acid, 4-hydroxy-, ethyl ester; benzoic acid, 4-hydroxy-, ethyl ester, sodium salt; benzoic acid, 4-hydroxy-, ethyl ester, potassium salt; benzoic acid, 4-hydroxy-, isopropyl ester:

Hazard

GHS Classification (Code)

Hazard Statement

Acute Aquatic

Category 2 (H401)

Toxic to aquatic life

Benzoic acid, 4-hydroxy-, propyl ester; benzoic acid, 4-hydroxy-, propyl ester, sodium salt; benzoic acid, 4-hydroxy-, propyl ester, potassium salt; benzoic acid, 4-hydroxy-, butyl ester; benzoic acid, 4-hydroxy-, butyl ester, sodium salt; and benzoic acid, 4-hydroxy-, isobutyl ester:

Hazard

GHS Classification (Code)

Hazard Statement

Acute Aquatic

Category 2 (H401)

Toxic to aquatic life

Chronic Aquatic

Category 3 (H412)

Harmful to aquatic life with long lasting effects.

Benzoic acid, 4-hydroxy-, phenylmethyl ester:

Hazard

GHS Classification (Code)

Hazard Statement

Acute Aquatic

Category 1 (H400)

Very toxic to aquatic life

Chronic Aquatic

Category 2 (H411)

Toxic to aquatic life with long lasting effects

Benzoic acid, 4-hydroxy-, heptyl ester; benzoic acid, 4-hydroxy-, octyl ester; benzoic acid, 4-hydroxy-, 2-isooctyl ester:

Hazard

GHS Classification (Code)

Hazard Statement

Acute Aquatic

Category 1 (H400)

Very toxic to aquatic life

Chronic Aquatic

-

Not classified

These classifications have been made based on the ecotoxicity data presented in this assessment. Data for the respective alkyl isomer has been read across to classify salts, with the resulting classifications consistent with all data considered in this assessment (including data not presented for some branched isomers). In some cases, data have been calculated. However, in these cases, the chemicals are expected to be well characterised by the structure-activity model used.

Chronic aquatic classifications were unable to be determined for heptyl-, octyl-, isooctyl- and laurylparaben due to insufficient data.

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Last update 5 November 2018