Is Sherwin-Williams Extreme Block Interior/Exterior Stain Blocking Alkyd Primer toxic?
No paint is risk-free, and "toxic" depends on how much you're exposed to and for how long. Here is what Sherwin-Williams's own documents show. Sherwin-Williams Extreme Block Interior/Exterior Stain Blocking Alkyd Primer scores 8 out of 100. Its untinted VOC is 338 g/L. Its Safety Data Sheet carries these warnings: cancer warning, reproductive warning and skin allergen. We found no third-party emissions testing for it.
- Health score
- 8
- VOC g/L
- 338
- Use
- Exterior primer, Interior primer
Safety Data Sheet warnings
- Cancer warningContains Methyl Ethyl Ketoxime N-Butan-2-ylidenehydroxylamine, bis(2-ethylhexanoate), a suspected carcinogen present in the paint itself, not only as dust.
- Reproductive warningSuspected of damaging fertility or the unborn child.
- Skin allergenMay cause an allergic reaction.
- FlammableKeep away from heat and flames.
- Aspiration hazardMay be fatal if swallowed and enters airways.
Evidence beyond the label
- Emissions testing: none found
- Health certification: none found
- Full ingredient list (Health Product Declaration): not published
Product
Updated October 12, 2026. Scores summarize the evidence makers publish. They don't guarantee safety or predict individual health outcomes. No brand pays to be listed. How we score