Acrylic acid

Acrylic acid was first synthesized from acetylene and carbon monoxide in the 1930s and later produced by the Reppe process from acetylene. [1] Modern industrial production uses the two-step catalytic oxidation of propylene (first to acrolein, then to acrylic acid), a process developed in the 1970s that is now nearly universal. Global production exceeds 6 million tons per year, with the vast majority converted to polyacrylates and superabsorbent polymers (SAP). SAPs — principally sodium polyacrylate — can absorb hundreds of times their own weight in water and are the core functional ingredient in disposable diapers, sanitary pads, and adult incontinence products. Other applications include surface coatings, adhesives (pressure-sensitive adhesives for tapes and labels), textile sizing, and water treatment polymers. Acrylic acid is a Hazardous Air Pollutant released from chemical manufacturing facilities — its high reactivity and tendency to polymerize exothermically make it a significant fire and explosion hazard in addition to a health hazard. [2] NTP bioassays found forestomach tumors in rodents from gavage administration, leading to the EPA probable carcinogen classification, though the forestomach mechanism is debated for its human relevance. [3]

Chemical plant workers manufacturing acrylic acid, polyacrylates, and superabsorbent polymers are occupationally exposed by inhalation of vapors and aerosols, and through skin and eye contact. Formulators creating acrylic acid-based adhesives, coatings, and caulks face exposures during product manufacture. The general public is not meaningfully exposed from finished polymer products (polymers are non-volatile and non-reactive compared to the monomer). Trace monomer residuals in consumer products (adhesives, coatings) are extremely low.

Acrylic acid is corrosive — concentrated solutions cause severe burns to skin, eyes, and respiratory tract. It is lachrymatory (causes tearing) at low vapor concentrations, providing irritant warning. At higher concentrations, severe respiratory tract damage can occur. The probable carcinogen classification is based on forestomach tumors in rodents, a location humans lack, making the human relevance uncertain. [2] Its polymerization hazard is extreme: if inhibitor (usually hydroquinone monomethyl ether) is absent or removed, acrylic acid can undergo violent runaway polymerization, generating dangerous heat and pressure.

Chemical plant workers in acrylic acid and polyacrylate manufacturing are most at risk. Workers formulating adhesives and coating resins using acrylic acid monomers face significant exposures. Emergency responders to acrylic acid spills or tank car incidents face severe acute exposure risk.

1. Industrial facilities must use corrosion-resistant materials, maintain inhibitor concentrations in stored monomer, and prevent temperature excursions that could trigger polymerization. 2. Workers must wear acid-resistant gloves (butyl rubber), face shields, and protective clothing; prevent ANY skin or eye contact. 3. Local exhaust ventilation is mandatory — the OSHA PEL is 10 ppm and the odor threshold is 1 ppm, providing warning. 4. Emergency eyewash and safety shower must be immediately accessible. 5. Personnel should be trained on acrylic acid polymerization hazards and emergency procedures.