potassium bromate

potassium bromate: I am wondering if it is safe/acceptable to order potassium bromate in solid form for a visually impressive science reaction for open day purposes. Are there any special considerations associated with this chemical, as I believe it can be quite hazardous? The teacher hopes to use the whole amount of potassium bromate ordered within a few days of ordering, so it would not be stored indefinitely in our chem room.

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Publication Date: 30 March 2015
Asked By: Anonymous
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potassium bromate

Thank you for taking the time to check on the appropriateness of the use of this chemical.  The response to your question is not a simple one. 

Summary Response:

Science ASSIST recommends that, in general, potassium bromate is not stored or used in schools. Potassium bromate KBrO3 is an extremely hazardous chemical. It is a very strong oxidising agent with the capacity to form explosive mixtures with combustible materials.  It is also extremely toxic and is classified as a carcinogen. Its main application seems to be as a reagent in the Belousov-Zhabotinsky (B-Z) “oscillating clock” chemical reaction. As potassium bromate is not an important chemical in the context of the school science curriculum, and as there are alternative “oscillating clock” reactions that use safer reagents, our current position, pending a final decision on our Recommended List of Chemicals, is that the limited applications for potassium bromate in school science do not justify the risks associated with its use.

If its use is contemplated, we strongly advise that this be subject to meeting the requirements of a strict, local risk assessment process, and then only as a demonstration activity undertaken by qualified staff.  Elements for consideration in a risk assessment would be the avoidance of any risk of human exposure to the chemical, the availability of similar demonstrations that use safer reagents, the disposal of unused potassium bromate and any wastes generated in the activity, purchase in minimum quantities, short-term storage of the chemical, and the levels of qualification and experience of staff proposing to undertake the activity. 

The proposed use for potassium bromate:

When the question was first raised, the Science ASSIST team was particularly concerned because at that stage there was no indication of the planned purchase quantity, management, or use, and no information as to the qualifications of the person(s) conducting the activity.  With just the information provided, we would strongly advise against the use of potassium bromate in a school.

Through further correspondence, we now understand that the proposed activity is the Belousov-Zhabotinsky (B-Z) chemical oscillating (“clock”) reaction that uses relatively small quantities, and will be conducted by a trained staff member at low temperatures and with minimal generation of vapours and using relevant Personal Protective Equipment (PPE).  These factors provide some reassurance that the activity can be safely managed, however, the use of safer alternative reactions is recommended.

Alternative “oscillating clock” demonstrations:

Two examples of alternative oscillating reactions:

Potassium bromate safety information:

Regarding the use of potassium bromate, it is the carcinogenic classification that raises the most serious concern for use in school science.  It is listed in the World Health Organisation's International Agency for Research on Cancer (IARC) Monographs on the evaluation of carcinogenic risks to humans as Group 2B (Possibly carcinogenic to humans). It is classified as Carcinogen Category 2 on the Safe Work Australia Hazardous Substances Information System (HSIS) with the new classification of Category 1B (presumed human carcinogen based on demonstrated animal carcinogenicity) under the GHS classification system.  It is very clear that any human exposure to this chemical is to be avoided. 

Potassium bromate carries the following GHS information:

  • Pictograms:
    • GHS 03 Flame over circle
    • GHS 06 Skull and crossbones
    • GHS 08 Health hazard
  • Signal Word “Danger”
  • Hazard Statements
    • May cause fire or explosion, strong oxidiser
    • May cause cancer
    • Toxic if swallowed
  • Precautionary Statements
    • Take any precautions to avoid mixing with combustibles
    • Wear fire/flame resistant/retardant clothing
    • Keep away from heat/sparks/open flames/hot surfaces. No smoking
    • If swallowed: immediately call a POISON CENTRE or doctor/ physician
    • Store locked up
    • Dispose of contents/container in accordance with local/regional/national/international regulations

Due to its carcinogenic category, its toxicity and its strong oxidising properties, if a school decides to use potassium bromate, it is essential that engineering controls, such as a fume cupboard is used and relevant PPE, such as safety glasses, gloves, lab coat and closed in shoes are worn when handling this chemical. Storage should be kept to minimum quantities in an appropriately labelled and sealed container, segregated from incompatible substances, as well as protected from sunlight and moisture in a secure chemical store.  If potassium bromate is purchased, then we recommend that schools minimise the management issues by purchasing a small pack size such as 100g rather than the more common 500g chemical pack size. 

Chemicals Approved for Use in Schools:

Science ASSIST has developed a list of recommended chemicals for use in schools.  Potassium bromate has been included on that list as it is acknowledged that there are currently a small number of carcinogenic chemicals that are commonly managed and used in senior school chemistry, with this use based on their specific relevance to the science curriculum, and on the lack of available safer substitutes. Potassium dichromate is an example. 

Hazardous Chemicals for Demonstration Purpose Use Only:

The Science ASSIST team recognises that there are some requirements for the special use of hazardous chemicals for demonstration purposes that lie outside usual student use and curriculum requirements.  It is not our intent to unnecessarily restrict such activities, but to support their safe conduct. 

In developing and maintaining the recommended list for schools, consideration is given to setting guidelines for such a category of chemicals. These quidelines include the following:

  • The school undertakes a detailed (written) Risk Assessment on the management, storage and use of the chemical prior to purchase. 
  • The teacher who is conducting the activity must be trained in its use.
  • Purchase can proceed only if the Risk Assessment indicates that there are adequate control measures for the storage, use and disposal of the chemical.
  • Purchase quantity is limited to the minimum available required for the planned activity.
  • After the activity, unused quantities of the chemical must be disposed of in an appropriate way, either immediately, when the teacher leaves employment at the school, or in any case within twelve months.

References

Chem-Supply Pty Ltd Safety Data Sheet: Potassium bromate, issue date 11/07/2013 https://www.chemsupply.com.au/documents/PO0163_AU.pdf

Chemwatch, Material Safety Data Sheet: Potassium bromate, issue date 25/1/2013 www.chemwatch.net  (subscription required)

IARC Monographs. Agents classified by the IARC Monographs. https://monographs.iarc.fr/agents-classified-by-the-iarc/ (Updated July 2018)

Safe Work Australia. 2015. GHS Hazardous Chemical Information List http://hsis.safeworkaustralia.gov.au/GHSInformation/GHS_Hazardous_Chemic...

Safe Work Australia. 2012. Guidance on the Classification of Hazardous Chemicals under the WHS Regulations http://www.safeworkaustralia.gov.au/sites/swa/about/publications/pages/g...

Safe Work Australia. 2014. Hazardous Substances Information System (HSIS) Consolidated Listing. http://hsis.safeworkaustralia.gov.au/ConsolidatedLists

Sigma Aldrich Safety Data Sheet: Potassium bromate, issue date 15/04/2013 http://www.sigmaaldrich.com/MSDS/MSDS/DisplayMSDSPage.do?country=AU&lang...

United Nations Institute for Training and Research (UNITAR). 2010. Understanding the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) A Companion Guide to the GHS Purple Book http://cwm.unitar.org/publications/publications/cw/ghs/GHS_Companion_Gui...                                                                                      

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