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Isocyanates

The reactive ingredient in spray foam, polyurethane, and one-part urethane sealants.

Building products and consumer items that commonly contain Isocyanates
Common building materials and consumer products containing Isocyanates

Toxic Chemical Databases

Where this family lands across the seven independent toxicology authorities we screen against.

LBC Red List
Listed
Prop 65
Not Listed
IARC
Listed
NTP RoC
Listed
GSPI
Not Listed
REACH SVHC
Listed
TSCA
Listed

Chemical Type

Highly Reactive Polyurethane Precursor

Chemical Description

Isocyanates are the high-energy "A-side" of every polyurethane reaction. The two families that matter in construction are MDI (methylene diphenyl diisocyanate) — the workhorse for spray foam insulation and engineered-wood adhesives — and TDI (toluene diisocyanate), still common in flexible foams and one-component urethane sealants. HDI shows up in two-part automotive-grade coatings. Once polyurethane is fully cured the bulk polymer is relatively stable, but partial-cure batches release residual monomer, oligomers, and amine catalysts for months to years. Isocyanates are the leading cause of occupational asthma in industrial countries, and once a person becomes sensitized, even trace exposure can trigger a severe attack. EBH does not install closed-cell or open-cell spray polyurethane foam in occupied homes. Where polyurethane chemistry is unavoidable (engineered-wood adhesives, urethane sealant beads), we specify products with documented low residual monomer and we cure them off-site.

Chemical Structure

Molecular schematic for Isocyanates — formula and structural features shown below.

−N=C=O
Methylene diphenyl diisocyanate (MDI) — OCN−C₆H₄−CH₂−C₆H₄−NCO · C₁₅H₁₀N₂O₂

Biological Activity

Severity scores summarize hazard endpoints from IARC, NTP, EPA IRIS, ATSDR, and NIOSH on a 0–10 scale. Mirrors the system-level output of our SDS Toxic Chemical Screener.

Respiratory
10/10
Immune
9/10
Skin
8/10
Cancer
5/10
Reproductive
5/10
Developmental
5/10
Endocrine
3/10
Neurological
4/10
Liver/Kidney
4/10
Cardiovascular
3/10

Chemical Analogs and Brand Names

Top Health Consequences

Pathways of Exposure

Substances in this Family

Each substance below has its own profile page with its own database flags, biological-activity scores, and exposure pathways — they are NOT interchangeable.

Building Materials with Isocyanates

Listed alphabetically. These are the product categories where this chemistry most often shows up — not an exhaustive list.

Want to screen a specific product? Drop the manufacturer's SDS into our SDS Toxic Chemical Screener — it runs every CAS number on the sheet against all seven databases shown above.