Household bleaches with concentration of active ingredient (sodium hypochlorite) less than 5.25% are not recommended to be used on a dilution ratio of 1:99 as an effective disinfectant.
Because of the germicidal property of household bleaches, the product is often used for environmental disinfection.
In a test on 29 models of household bleach, the Consumer Council has found that many of the samples were not up to 5.25% in concentration.
In the Government health advice, the public is urged to mix one part of household bleach with 99 parts of water for environmental disinfection in the fight against the menace of the human swine flu.
The test showed that only 8 out of 29 samples of household bleach contained sodium hypochlorite at concentration of 5.25% on which the 1:99 ratio is based for use as an effective disinfectant.
3 of the samples were marginally under while the remainders (18) of the models had concentration levels of only 1% to 4.8%.
The dilution ratio of 1:99 on household bleaches with concentration at 5.25% will translate into approximately 500ppm chlorine, which is considered appropriate for general environmental cleaning.
To disinfect surfaces or objects contaminated with vomitus, excreta or secretions, a dilution ratio of 1:49 which will translate into approximately 1,000ppm chlorine is recommended.
Sodium hypochlorite is unstable and will decompose over time. Consumer should be aware of the varying concentrations and dilute bleach properly when product with lower concentration of active ingredient is used.
Of the 29 models, 16 were labelled with the percentage of sodium hypochlorite concentration. But when put to the test, 11 of them were found to contain less than the claimed amount, the discrepancy ranging from 5% to 36%.
The test findings were forwarded to the Customs and Excise Department (C&ED) for consideration if such may constitute a violation under the Trade Descriptions Ordinance.
Besides the concentration of active ingredient, labelling information such as the manufacturing date/expiry date, bilingual safety warning, and design of the cap are equally important.
9 samples were without any indication of the manufacturing date or expiry date - incidentally, some were among the lowest amount of sodium hypochlorite samples detected. This may be due to prolonged storage period or even beyond expiration.
Further, only 7 of the 29 samples were designed with children safety cap to prevent children from opening it easily. However, 3 of them were found to function improperly - the cap could be opened easily even without pushing down and twisting it at the same time. 4 of the samples were also found to carry no safety warning in English.
The findings were forwarded to the C&ED for investigation of any contravention under the Consumer Goods Safety Ordinance.
In view of the variances in sodium hypochlorite concentration of household bleaches available in the market, consumers are advised that in order to achieve optimal effectiveness in disinfection, they should adjust the amount required accordingly if the household bleach is above or below the 5.25% concentration.
Consumers are advised also not to purchase household bleaches in excessive quantity as sodium hypochlorite is unstable and will decompose over time.
Precautions in use of household bleach as disinfectant:
- Do not mix with acid or other household cleaners (such as drain cleaners, toilet cleaners, metal cleaners, wax removers, glass cleaners and oven cleaners, etc.) as it may generate toxic chlorine gas and other harmful chemicals.
- Dilute with cold water, instead of warm or hot water, otherwise, it may affect the disinfecting efficacy due to decomposition of the active ingredient.
- Dilute and use in well-ventilated area.
- Store in cool and dry place, avoid direct sunlight or any other heat source.
- Store in place that children cannot reach.
- Diluted solution should be used as soon as possible, and best within 24 hours to achieve effective disinfection.
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