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Alkaline Salts-Carbonates: Human health tier II assessment

07 February 2014

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Chemicals in this assessment

Chemical Name in the Inventory CAS Number
Carbonic acid, disodium salt 497-19-8
Carbonic acid, dipotassium salt 584-08-7

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.

Grouping Rationale

This group of two chemicals, sodium carbonate and potassium carbonate, consists of simple salts that have local irritant properties relating to their strong alkalinity, but have low systemic toxicity. These chemicals have been grouped together for assessment due to their similarity in intrinsic properties (corrosivity based on high pH and high alkali reserve), uses (such as a buffering agent in cosmetics, and domestic detergents and cleaners), and potential for local health effects due to the basicity of carbonates (NICNAS, 2012).

Australian

Both chemicals in this group are listed on the 2006 High Volume Industrial Chemicals List (HVICL) (NICNAS, 2006).

The chemicals have reported uses including:

  • in cleaning agents and additives;
  • in dishwashing and laundry detergents;
  • as photochemicals;
  • as fillers;
  • as laboratory chemicals; and
  • as a pH-regulating/buffering agent in cosmetic products.

International

The following international uses have been identified through European Union Registration, Evaluation and Authorisation of Chemicals (EU REACH) dossiers; the Organisation for Economic Cooperation and Development Screening information data set International Assessment Report (OECD SIAR); Galleria Chemica; Substances and Preparations in the Nordic countries (SPIN) database; the European Commission Cosmetic Ingredients and Substances (CosIng) database; United States (US) Personal Care Product Council International Nomenclature of Cosmetic Ingredients (INCI) Dictionary; and eChemPortal: OECD High Production Volume chemical program—OECD HPV, the US Environmental Protection Agency's Aggregated Computer Toxicology Resource—ACToR, the US National Library of Medicine's Hazardous Substances Data Bank—HSDB, and the US Department of Health and Human Services—Household Products Database.

Both chemicals have many industrial uses. The most common uses are described below.

The chemicals have reported cosmetic use including:

  • as buffering agents;
  • as bulking agents; and
  • in soap, fragrance, perfume and deodoriser manufacture.

The chemicals have reported domestic use including in:

  • cleaning/bleaching agents;
  • dishwashing detergents;
  • laundry detergent; and
  • paints, lacquers and varnishes.

The chemicals have reported commercial use including:

  • in anti-freezing agents;
  • in adhesive and binding agents;
  • in flame retardants and extinguishing agents;
  • in manufacturing sodium salts;
  • in manufacting glass;
  • in petroleum refining;
  • in the production of sodium chromate, sodium silicate and sodium bicarbonate;
  • in pulp and paper manufacture;
  • in surface treatment;
  • in textile bleaches;
  • in tanning and leather finishing applications;
  • as absorbents and adsorbents;
  • as fillers;
  • as photochemicals; and
  • as process regulators.

The chemicals have reported site-limited use including in complexing and flocculating agents.

Australian

The chemical is listed in the Poisons Standard (SUSMP—Standard for Uniform Scheduling of Medicines and Poisons) in Schedules 5 and 6, and Appendix C.

'Schedule 5 Alkaline salts, being the carbonate, silicate or phosphate salts of sodium or potassium alone or in any combination:

(a) in solid orthodontic device cleaning preparations, the pH of which as an "in-use" aqueous solution is more than 11.5;

(b) in solid automatic dishwashing preparations, the pH of which in a 500 g/L aqueous solution or mixture is more than 11.5 but less than or equal to 12.5;

(c) in other solid preparations, the pH of which in a 10 g/L aqueous solution is more than 11.5; or

(d) in liquid or semi-solid preparations, the pH of which is more than 11.5, unless:

     (i) in food additive preparations for domestic use; or

     (ii) in automatic dish washing preparations for domestic use with a pH of more   than 12.5, except when separately specified in these Schedules.'

'Schedule 6  Alkaline salts, being the carbonate, silicate or phosphate salts of sodium or potassium alone or in any combination for non-domestic use:

(a) in solid automatic dishwashing preparations, the pH of which in a 500 g/L aqueous solution or mixture is more than 12.5; or

(b) in liquid or semi-solid automatic dishwashing preparations, the pH of which is more than 12.5.'

'Appendix C Alkaline salts, being the carbonate, silicate or phosphate salts of sodium or potassium alone or in any combination for domestic use:

(a) in liquid or semi-solid food additive preparations, the pH of which is more than 11.5;

(b) in solid automatic dishwashing preparations, the pH of which in a 500 g/L aqueous solution or mixture is more than 12.5; or

(c) in liquid or semi-solid automatic dishwashing preparations, the pH of which is more than 12.5.'

The SUSMP also recommends appropriate ‘Warning Statements’ and ‘Safety Directions’ for alkaline salts when used in consumer products.  

International

No international restrictions were identified.

Existing Worker Health and Safety Controls

Hazard Classification

Sodium carbonate is classified as hazardous, with the following risk phrases for human health in the Hazardous Substances Information System (HSIS) (Safe Work Australia):

'Xi; R36 (Irritating to eyes)'.

There is no human health classification for potassium carbonate in the HSIS.

Australian

Sodium carbonate has an exposure standard of 7.5 mg/m³ (5 ppm) time weighted average (TWA) and 15 mg/m³ (10 ppm) short-term exposure limit (STEL) (Safework Australia).

No specific exposure standards are available for potassium carbonate.

International

Occupational exposure standard limits for sodium and potassium carbonate recommended by other countries are provided below (Galleria Chemica, 2013):

'US Dept of Energy (DOE) Temporary Emergency Exposure Limits (TEELs):

Sodium carbonate: TEEL-0 = 10 mg/m³ , TEEL-1 = 30 mg/m³ , TEEL-2 = 50 mg/m³ , TEEL-3 = 500 mg/m³

Potassium carbonate: TEEL-0 = 10 mg/m³ , TEEL-1 = 20 mg/m³ , TEEL-2 = 150 mg/m³ , TEEL-3 = 500 mg/m³'

No other country has an occupational exposure limit specifically for sodium and potassium carbonate, although many countries have assigned a generic TWA exposure limits of 10 mg/m³  (inhalable dust), and 3 mg/m³ (respirable dust) for particles not otherwise classified (PNOC).

Toxicokinetics

When sodium or potassium carbonate comes into contact with liquids, including body fluids, they dissociate into sodium and carbonate ions, or potassium and carbonate ions, respectively. Carbonate ions are neutralised by the gastric acids in the stomach resulting in the formation of bicarbonate ions and/or carbon dioxide (CO2). In the body, the speciation of carbonate as pH-dependent CO2 from the tissues, diffuses rapidly into the red blood cells, where it is hydrated to form carbonic acid. The formed carbonic acid dissociates into bicarbonate and hydrogen ions. Most of the bicarbonate ions diffuse into the plasma and are excreted as respiratory CO2 (OECD, 2002; REACH a & b, HSDB).  The carbonate ion is a strong base, and the pure chemicals and concentrated solutions are highly akaline. If, on ingestion of these chemicals, the resulting increase in pH is too great for the body's buffering system to regulate, the body's physiological pH may become slightly alkaline, resulting in alkalosis.

Sodium and potassium carbonates are therefore expected to only show local toxic effects from all routes of exposure.

Oral

In animal tests, both chemicals were of low acute toxicity following oral exposure. The median lethal dose (LD50) was >2000 mg/kg bw in rats (OECD, 2002;  REACHa; REACHb).

The majority of the animals that died following acute oral exposure to sodium carbonate at concentrations up to 2600 mg/kg/bw showed oral or nasal discharge, lesions in the liver, mottled lungs, mottled or pale kidneys and a red or partly gas-filled gastro-intestinal tract. No death occurred following treatment with potassium carbonate at concentrations up to 2000 mg/kg bw; however, piloerection was observed.

Dermal

In animal tests, both chemicals were of low acute toxicity following dermal exposure. The median lethal dose (LD50) was >2000 mg/kg bw in rats (OECD, 2002; REACHa; REACHb).

No systemic effects were observed following dermal exposure to sodium or potassium carbonate. Local severe skin irritation (severe erythema and oedema) was seen at the application site (OECD, 2002;  REACHa; REACHb).

Inhalation

In animal tests, both chemicals were of low acute toxicity following inhalation exposure. The median lethal dose (LC50) was >2000  mg/m3  in rats (OECD, 2002;  REACH, a & b).

Signs of respiratory impairment including dyspnoea, wheezing, excessive salivation and a distended abdomen were observed immediately after inhalation exposure to sodium carbonate of up to 2300 mg/m3. Excessive salivation, repeated swallowing and a lack of appetite were observed 2–5 hours after exposure. Animals that died had lesions in the anterior trachea, posterior pharynx and larynx, along with an accumulation of mucus, vesiculation and mucosal oedema (REACHa).

No mortalities were observed when rats were exposed to approximately 4.6 mg/L of potassium carbonate. Decreased activity, irregular respiration, hunched posture and lethargy were noted following exposure. Within 24 hours of exposure, the corrosive nature of potassium carbonate manifested in the form of dermal necrosis and corneal opacity, which were noted in all animals. Corrosive effects were most severe around the mouth and on the forelimbs (REACHb).

Observation in humans

Eight children were hospitalised after ingesting or inhaling laundry detergent powder containing sodium carbonate. Adverse effects such as stridor (a high-pitched wheezing sound), drooling and respiratory distress were reported (HSDB).

Corrosivity

Aqueous solutions of sodium and potassium carbonates are strongly alkaline with the pH of saturated solutions calculated to be 12.32 (UC Davis ChemWiki, 2013). Concentrated solutions tend to produce local necrosis of mucous membranes. Ingestion of large quantitites may produce corrosion of the gastrointestinal tract, vomiting, diarrhoea, circulatory collapse and even death.

Exposure to dusts of sodium and potassium carbonate may cause dermal necrosis, corneal opacity and irritation of the mucous membranes with subsequent coughing and shortness of breath (OECD, 2002; REACHa; REACHb).

Respiratory Irritation

Studies for the respiratory irritation effect of sodium or potasium carbonate are not available. Both chemicals are strongly alkaline and concentrated solutions can produce corrosive effects.

Following acute inhalation exposure to either chemical, respiratory impairment was noted. In addition, acute inhalation exposure to potassium carbonate resulted in dermal necrosis and corneal opacity in all animals. Corrosive effects were severe around the mouth and on the forelimbs (REACHa; REACHb).

Histopathological changes of the respiratory tract and the lungs were considered local responses to the high alkalinity of this group of chemicals following repeated inhalation exposure (REACHa; REACHb).

These effects were sufficient to warrant a health hazard classification.

Skin Irritation

In several animal studies, sodium and potassium carbonates were reported to have irritative and corrosive effects to abraded skin and to be slightly irritant to intact skin, depending on the concentration of the chemical and the length of skin contact. In an acute dermal study in rabbits, severe erythema and oedema were observed in all animals following 24 hours of exposure to sodium carbonate (REACHa; REACHb).

The skin irritation effects seen in the irritation studies do not meet the criteria for the HSIS skin irritation classification. However, both chemicals are strongly alkaline and long-term  exposure to solid or concentrated solutions are likely to produce serious skin irritation or corrosive effects. Furthermore, observations in humans indicate that both chemicals are corrosive to mucous membranes.

Overall, the above skin irritation effects were not sufficient to warrant a hazard classification.

Eye Irritation

Sodium carbonate is classified as hazardous with the risk phrase 'Irritating to eyes' (Xi; R36) in HSIS (Safe Work Australia). However, in several eye irritation studies in rabbits, sodium carbonate was found to be severely irritating to the eyes, with effects including conjunctivitis, marked corneal opacity and iritis, which persisted for seven days (REACHa; REACHb). The available data support an amendment to the current HSIS eye irritation classification for sodium carbonate.

In several studies in rabbits, potassium carbonate was reported to be severely irritating to the eyes with irritation effects including conjunctival redness, chemosis with moderate secretion, and corneal opacity. Iritis was observed also in all animals. Effects on the cornea, conjunctiva and iris persisted for seven days. In another eye irritation study, a 3 % potassium carbonate solution was considered a severe eye irritant when tested according to OECD Test Guideline (TG) 473 (REACHb; HSDB).

Based on the severe irritation effects on the conjunctivae, cornea and iris, which persisted up to seven days in rabbits, both chemicals warrant classification as hazardous with the risk phrase 'Risk of serious damage to eyes' (Xi;R41) in HSIS (Safe Work Australia).

Observation in humans

The alkalinity of sodium carbonate can cause injury to the corneal epithelium. Reported instances of permanent corneal opacification were caused not by the pure chemical, but by a splash of molten chemical at 820°C and by a mixture that also contained calcium hydroxide (OECD, 2002).

Human patch test studies of sodium carbonate showed no irritation reactions on intact skin. However, abraded skin showed erythema and oedema (REACHa).

Twenty-seven army inductees assigned to dish washing, immersed their bare hands for four to eight hours in hot water containing a detergent blend that included sodium carbonate. All subjects developed irritation on the exposed surfaces. Vesicles and large blisters were reported within 10 to 12  hours after exposure. Subungual purpura (bleeding under the fingernails) and secondary infections were also noted in several individuals (REACHa).

The reported human findings on skin and eye irritation support the animal findings.

Skin Sensitisation

Based on the limited data available, the chemicals in this group are not considered to be skin sensitisers (OECD, 2002; REACHa; REACHb). No structural flags for sensitisation are present.

Oral

No data are available. Due to the biological importance of the products formed by the stomach acid (biocarbonate and carbon dioxide), systemic toxicity is not expected.

Dermal

No data are available.

Inhalation

In rats, histopathological changes of the respiratory tract and the lungs were seen following repeated inhalation exposure to sodium carbonate (70 mg/m3 aqueous sodium cabonate at pH 11.6 for 3.5 months) and potassium carbonate (0.4 mg/L potassium carbonate at pH 9.9 for 21days). These effects were considered local responses to the high alkalinity of this group of chemicals (OECD, 2002; REACHa; REACHb).  

Genotoxicity

Based on the available data, the chemicals in this group are not considered to be genotoxic (OECD, 2002; REACHa; REACHb). Carbonate ions are neutralised under physiological conditions to form bicarbonate ions and/or carbon dioxide, which are major products of all human metabolic activities; therefore, systemic toxicity is not expected.

Carcinogenicity

No data are available. Based on the available data from carcinogenicity studies with related substances (sodium bicarbonate and potassium bicarbonate), the chemicals in this group are not considered carcinogenic (OECD, 2002; REACHa; REACHb). Carbonate ions are neutralised under physiological conditions to form bicarbonate ions and/or carbon dioxide, which are major products of all human metabolic activities; therefore, systemic toxicity is not expected.

Based on the limited information available, the chemicals in this group do not show specific reproductive or developmental toxicity (OECD, 2002; REACHa; REACHb). Carbonate ions are neutralised under physiological conditions to form bicarbonate ions and/or carbon dioxide, which are major products of all human metabolic activities; therefore, systemic toxicity is not expected.

Critical Health Effects

The critical health effects for risk characterisation include serious eye damage and respiratory irritation because of the high basicity of the chemicals in this group. Skin irritation, and corrosion of eyes and mucous membranes are also of concern where long-term exposure to the solid or concentrated solutions may occur. These effects are particularly relevant to domestic use of the chemicals.

Public Risk Characterisation

The general public may be exposed to the chemical through oral, dermal, ocular and/or inhalation routes when using cosmetic and domestic products containing this group of chemicals. Of particular concern is the possibility of ingestion of highly alkaline dishwashing products by children, whereas cosmetic products containing the chemicals are not expected to exhibit extreme pH.

The chemical is currently listed on Schedules 5, 6 and Appendix C of the SUSMP. A number of warning statements, first aid instructions and safety directions relating to the alkalinity of the chemicals apply. The current controls are considered adequate to minimise the risk to public health posed by cosmetic and domestic products containing the chemical: therefore, the chemical is not considered to pose an unreasonable risk to public health.

Occupational Risk Characterisation

Given the critical local health effects, the chemicals may pose an unreasonable risk to workers unless adequate control measures to minimise dermal, ocular and inhalation exposure to the chemicals are implemented. The chemicals should be appropriately classified and labelled to ensure that a person conducting a business or undertaking (PCBU) at a workplace (such as an employer) has adequate information to determine appropriate controls.

The data available support an amendment to the hazard classification in HSIS (refer to the Recommendation section).

NICNAS Recommendation

Assessment and risk management of these chemicals are considered to be sufficient, provided that the recommended amendment to the HSIS classification is adopted, and labelling and all other requirements are met under workplace health and safety and poisons legislation as adopted by the relevant state or territory.

Public Health

Products containing these chemicals should be labelled in accordance with state and territory legislation (SUSMP).

Work Health and Safety

Both chemicals are recommended for classification and labelling under the current approved criteria and adopted GHS as below. This assessment does not consider classification of physical hazards and environmental hazards.

Hazard Approved Criteria (HSIS)a GHS Classification (HCIS)b
Irritation / Corrosivity Risk of serious eye damage (Xi; R41) Irritating to respiratory system (Xi; R37) Causes serious eye damage - Cat. 1 (H318) May cause respiratory irritation - Specific target organ tox, single exp Cat. 3 (H335)

a Approved Criteria for Classifying Hazardous Substances [NOHSC:1008(2004)].

b Globally Harmonized System of Classification and Labelling of Chemicals (GHS) United Nations, 2009. Third Edition.

* Existing Hazard Classification. No change recommended to this classification

Advice for consumers

Products containing these chemicals should be used according to the instruction on the label.

Advice for industry

Control measures

Control measures to minimise the risk from oral, dermal, ocular and inhalation exposure to these chemicals should be implemented in accordance with the hierarchy of controls. Approaches to minimise risk include substitution, isolation and engineering controls. Measures required to eliminate or minimise risk arising from storing, handling and using a hazardous chemical depend on the physical form and the manner in which the chemical is used. Examples of control measures which may minimise the risk include, but are not limited to:

  • using closed systems or isolating operations;
  • using local exhaust ventilation to prevent the chemical from entering the breathing zone of any worker;
  • air monitoring to ensure control measures in place are working effectively and continue to do so;
  • minimising manual processes and work tasks through automating processes;
  • work procedures that minimise splashes and spills;
  • regularly cleaning equipment and work areas; and
  • using protective equipment that is designed, constructed, and operated to ensure that the worker does not come into contact with the chemical.

Guidance on managing risks from hazardous chemicals are provided in the Managing risks of hazardous chemicals in the workplace—Code of practice available on the Safe Work Australia website.

Personal protective equipment should not solely be relied upon to control risk and should only be used when all other reasonably practicable control measures do not eliminate or sufficiently minimise risk. Guidance in selecting personal protective equipment can be obtained from Australian, Australian/New Zealand or other approved standards.

Obligations under workplace health and safety legislation

Information in this report should be taken into account to assist with meeting obligations under workplace health and safety legislation as adopted by the relevant state or territory.  This includes, but is not limited to:

  • ensuring that hazardous chemicals are correctly classified and labelled;
  • ensuring that (material) safety data sheets ((m)SDS) containing accurate information about the hazards (relating to both health hazards and physicochemical (physical) hazards) of the chemical are prepared; and
  • managing risks arising from storing, handling and using a hazardous chemical.

Your work health and safety regulator should be contacted for information on the work health and safety laws in your jurisdiction.

Information on how to prepare an (m)SDS and how to label containers of hazardous chemicals are provided in relevant codes of practice such as the Preparation of safety data sheets for hazardous chemicals—Code of practice and Labelling of workplace hazardous chemicals—Code of practice, respectively. These codes of practice are available from the Safe Work Australia website.

A review of the physical hazards of the chemical has not been undertaken as part of this assessment.

References

Galleria Chemica. Accessed May 2013 at http://jr.chemwatch.net/galleria/

Hazardous Substances Data Bank (HSDB). National Library of Medicine. Accessed May 2013 at http://toxnet.nlm.nih.gov.

National Industrial Chemicals Notification and Assessment Scheme (NICNAS) 2012. Inventory Multi-Tiered Assessment and Prioritisation Framework: Identification of chemicals of low concern to human health.  Australian Government Department of Health and Ageing.  Accessed May 2013 at  http://www.nicnas.gov.au.

NICNAS 2006. Australian High Volume Industrial Chemicals List (AHVICL). Accessed April 2013 at http://www.nicnas.gov.au/Industry/Australian_High_Volume_Industrial_Chemicals/NICNAS_AHVICL_2006_PDF.pdf

OECD 2002. Screening Information Data Set (SIDS) Initial assessment Report (SIAR). Sodium carbonate. OECD, Paris. Accessed April 2013 at http://www.inchem.org/documents/sids/sids/Naco.pdf

REACH 2013a. Registration, Evaluation and authorisation of Chemicals (REACH) Dossier. Sodium Carbonate (CAS RN 497-19-8). Accessed 2013 at http://echa.europa.eu/web/guest/information-on-chemicals/registered-substances

REACH 2013b. Registration, Evaluation and authorisation of Chemicals (REACH) Dossier. Potassium Carbonate (CAS RN 584-08-7). Accessed May 2013 at http://echa.europa.eu/web/guest/information-on-chemicals/registered-substances

Safe Work Australia (SWA). Hazardous Substances Information System (HSIS). Accessed April 2013 at http://hsis.safeworkaustralia.gov.au/HazardousSubstance

UC Davis ChemWiki 2013. Weak Acid and Bases. Accessed 11 December 2013 at http://chemwiki.ucdavis.edu/?title=Physical_Chemistry/Acids_and_Bases/Ionization_Constants/Acid_and_Base_Strength/Weak_Acids_%26_Bases.

Last Update 07 February 2014