top of page

Why Health Science Authority (HSA)
Issued a Class 2 Recall Of
Hand Sanitisers In Singapore?

18 brands of hand sanitisers were issued with a Class 2 recall by HSA in Singapore. Many are concern and are circulating the news through social media.  We try to answer some of the questions you may have.
Note: Class 2 Recall is for recalls of products with issues that would not likely cause serious adverse health outcomes.

Glass of Milk

Reason for Recall ?

Presence of harmful substances found in

these hand sanitisers:

Acetaldehyde  &  Methanol

Hand Sanitizer
Hand Sanitizer

What exactly are acetaldehyde and methanol?

Acetaldehyde or ethanal is a low molecular weight aldehyde. Acetaldehyde occurs naturally in coffee, bread, and ripe fruit and is produced by plants[1]. It is also produced by the partial oxidation of ethanol by the liver enzyme alcohol dehydrogenase and is a contributing cause of hangover after alcohol consumption[1].

Methanol is the smallest alcohol usually petroleum-derived. Petronas is one of largest producers and methanol is used in a wide range of applications from polymers, adhesives, fuel cells and also as base chemicals for pharmaceutical and agrichemicals. It is also used as a denaturant in ethanol for some industry application.

to start editing the content and make sure to add any relevant details or information that you want to share with your visitors.

How can acetaldehyde and methanol be present in hand sanitisers?

Ethanol is a common base alcohol used in hand sanitisers. Most ethanol is produced by fermentation process of sugar content crops such as sugar cane.

The first step of the alcoholic fermentation pathway involves pyruvate, which is formed by yeast[2]. In the following step, the pyruvate is decarboxylated to acetaldehyde in a reaction that is catalyzed by the enzyme pyruvate decarboxylase[2]. The acetaldehyde is then reduced to ethanol, which is catalyzed by alcohol dehydrogenase[2]. If the ethanol is not purified properly, acetaldehyde can be present in the final product ethanol in significant levels.


Figure 1: Alcoholic fermentation (Ciani 2008) [2].

Methanol is the cheapest alcohol and it is toxic. It can be found in ethanol as a denaturant, usually at 5% concentration. It is also known that methanol is used as an adulterant in alcohol based sanitisers and disinfectants as methanol can be 5 to 10 times cheaper than ethanol or propyl alcohol.

Image by Nathan Dumlao
Doctor Analyzing X-Rays

Why acetaldehyde and methanol are dangerous?

Acute (short-term) exposure to acetaldehyde results in effects including irritation of the eyes, skin, and respiratory tract[3]. Symptoms of chronic (long-term) intoxication of acetaldehyde resemble those of alcoholism[3]. International Agency Research on Cancer (IARC) has classified acetaldehyde in Group 2B Agents which is possibly carcinogenic to humans[4].

Substantial methanol exposure can result in nausea, vomiting, headache, blurred vision, permanent blindness, seizures, coma, permanent damage to the nervous system or death[5].

What are the occupational exposure limits (OEL) of acetaldehyde & methanol
[6] [7]?

In general, the occupational exposure limit (OEL) represents the maximum concentration of a toxic substance to which a worker can exposed over a period of time without suffering any harmful consequences. Table below shows the OEL for acetaldehyde and methanol in ppm level, in which 1% is equivalent to 10000 ppm.


OSHA: Occupational Safety and Health Administration

PEL: Permissible Exposure Limit

NIOSH: National Institute for Occupational Safety and Health

REL: Recommended Exposure Limit

TWA: Time-Weighted Average

ACGIH: American Conference of Governmental Industrial Hygienists

TLV: Threshold Limit Value

STEL: Short Term Exposure Limit

Image by Gayatri Malhotra
Scientist Pipetting

What is the safe limit of acetaldehyde and methanol in ethanol?

According to United State Pharmacopeia (USP), the acceptance limit for acetaldehyde and methanol is 10 ppm and 200 ppm respectively[8]. However, US FDA(Food and Drug Administration) has relaxed the limit in “Temporary Policy for Preparation of Certain Alcohol-Based Hand Sanitiser Products During the Public Health Emergency (COVID-19)” as stated in table below to secure the supply of the hand sanitiser across the country. This change allows small amounts of impurities to be in sanitiser products that are produced often through ethanol production.

[1] Michael Uebelacker, Dirk W. Lachenmeier, Quantitative Determination of Acetaldehyde in Foods UsingAutomated Digestion with Simulated Gastric Fluid Followed by Headspace Gas Chromatography, Journal of Analytical Methods in Chemistry, 2011, 1-13.
[2] M. Ciani, F. Comitini, I. Mannazzu, Fermentation, Encyclopedia of Ecology, 2013, 2, 1548-1557.
[3] Acetaldehyde, Hazard Summary, United States Environmental Protection Agency (US EPA).
[4] Agents Classified by the IARC Monographs, International Agency for Research on Cancer (IARC), 2018, Volumes 1–123.
[5] Methanol: Systemic Agent, Centers for Disease Control and Prevention (CDC).
[6] Permissible Exposure Limits – Annotated Tables, Occupational Safety and Health Administration (OSHA).
[7] Methyl Alcohol, NIOSH Pocket Guide to Chemical Hazards, Centers for Disease Control and Prevention (CDC).
[8] Excerpted USP-NF and FCC Standards, A Hand Sanitiser Resource, United States Pharmacopeia (USP), 2020.
[9] Temporary Policy for Preparation of Certain Alcohol-Based Hand Sanitiser Products During the Public Health Emergency (COVID-19), United States Food and Drug Administration (US FDA), 2021.

bottom of page