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We Ranked 47,000 Chemicals in Korea's Database. Only 3 Hit the Top.

Korea's chemical substance database tracks over 47,000 substances. Each one can carry up to 9 regulatory flags — toxic, restricted, prohibited, priority management, accident preparedness, CMR (carcinogenic/mutagenic/reprotoxic), registration required, persistent organic pollutant, and Rotterdam Convention substance.

We queried the entire database and ranked every substance by the number of simultaneous classifications it carries. The result: out of 47,000+ substances, only three carry 5 flags. No substance carries more than 5.

The three most classified substances

1. Formaldehyde — CAS 50-00-0

Flag Details
Toxic Acute toxicity 1%, chronic toxicity 0.1%
Restricted Banned in furniture veneer, textiles, children's products (age 3 and under), wallpaper paste, leather softeners at 1%+
Priority management Flagged as CMR
Accident preparedness Emergency plans required for facilities handling 1%+ mixtures
Registration required Must be registered before commercial use

Formaldehyde is the only substance in the database that is simultaneously toxic, restricted, a priority substance, an accident preparedness substance, and registration-required. We covered its regulations in detail in our previous article on everyday chemicals.

The International Agency for Research on Cancer (IARC) classifies formaldehyde as a Group 1 carcinogen.

2. PFOS (potassium salt) — CAS 2795-39-3

Flag Details
Toxic Acute toxicity 25%, chronic toxicity 0.3%
Priority management Flagged as CMR and STOT (specific target organ toxicity)
CMR Classified under the CMR category
Persistent organic pollutant Handling restricted under Korea's Persistent Organic Pollutants Act
Rotterdam Convention Listed as internationally regulated substance

PFOS — perfluorooctanesulfonate — belongs to the PFAS family, sometimes called "forever chemicals" because they do not break down in the environment. PFOS was widely used in firefighting foams, textile waterproofing, and electronics manufacturing.

The Stockholm Convention on Persistent Organic Pollutants listed PFOS for global restriction in 2009. Korea classifies it as a persistent organic pollutant with restricted handling.

What makes PFOS unusual in the database is its combination of domestic toxicity flags (toxic + priority + CMR) with international treaty flags (persistent + Rotterdam). Most substances carry one or the other. PFOS carries both.

3. HBCD — CAS 25637-99-4 / 3194-55-6

Flag Details
Toxic Ecological toxicity 2.5%
Priority management Flagged as CMR and PBT (persistent, bioaccumulative, toxic)
Registration required Must be registered before commercial use
Persistent organic pollutant Handling banned under Korea's Persistent Organic Pollutants Act
Rotterdam Convention Listed as internationally regulated substance

HBCD — hexabromocyclododecane — is a brominated flame retardant. It was used primarily in polystyrene insulation panels for construction, and also in electronics, textiles, and upholstered furniture. Global production reached approximately 28,000 tonnes per year before restrictions took effect.

The Stockholm Convention listed HBCD for global elimination in 2013. Korea's classification reflects this: HBCD is the only substance among the top three where handling is fully banned under the Persistent Organic Pollutants Act, compared to PFOS which is restricted but not banned.

Two CAS numbers (25637-99-4 and 3194-55-6) appear in the database for HBCD. Both carry identical regulatory classifications.

The 4-flag tier

Below the top three, substances with 4 flags form a larger group. Most are lead compounds, chromium compounds, and cadmium compounds. Two that most people would recognize:

Carbon monoxide (CO) — CAS 630-08-0

Flag Details
Toxic Acute toxicity 25%, chronic toxicity 0.3%
Priority management Flagged as CMR and STOT
Accident preparedness Emergency plans required for facilities handling 25%+ mixtures
CMR Classified under the CMR category

Carbon monoxide is a byproduct of incomplete combustion — car exhaust, gas heaters, charcoal grills.

Vinyl chloride — CAS 75-01-4

Flag Details
Toxic Chronic toxicity 0.1%
Priority management Flagged as CMR
Accident preparedness Emergency plans required for facilities handling 0.1%+ mixtures
Registration required Must be registered before commercial use

Vinyl chloride is the raw material for PVC (polyvinyl chloride), one of the most widely produced plastics in the world. It is a known human carcinogen. Korea's accident preparedness threshold for vinyl chloride is 0.1% — much lower than carbon monoxide's 25%.

What the ranking reveals

Formaldehyde's 5 flags come entirely from Korea's domestic chemical management laws. PFOS and HBCD both carry flags tied to international treaties — the Stockholm Convention (persistent organic pollutant) and the Rotterdam Convention — on top of their domestic classifications.

No substance in the database carries 6 or more flags out of a possible 9.

Flags Count Examples
5 3 substances Formaldehyde, PFOS, HBCD
4 ~30+ substances Carbon monoxide, Vinyl chloride, Cadmium, Lead, Chrysotile, Carbon tetrachloride
3 Hundreds Various industrial chemicals
1–2 Tens of thousands Majority of the database

Most substances carry 1 or 2 flags. Five is the ceiling.

Methodology and Sources

Regulatory classifications were queried from a structured database of K-REACH chemical substances. Each substance's 9 binary classification flags were summed and ranked. The top 30 results were analyzed for this article.

International context is based on the Stockholm Convention on Persistent Organic Pollutants (official treaty text and listed substances) and the Rotterdam Convention on the Prior Informed Consent Procedure.

The database is available through the K-REACH Chemical Substance API on RapidAPI.

Important Notice: This article is for informational purposes only. It is not legal, regulatory, or medical advice. Chemical regulations change frequently — always verify current status against official sources before making business or compliance decisions. For full terms, see our Disclaimer.

Decoded Korea publishes data-driven analysis of Korean cosmetic ingredients, chemical regulations, and safety data.

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