Effects of poly(acrylic acid)'s crosslinker content on pulmonary toxicity in rats.

For many years, poly(acrylic acid) (PAA) was considered an almost perfectly safe material, but in 2017, reports surfaced of pulmonary toxicity in workers who had handled crosslinked PAA particles at a Japanese factory. To elucidate the chemical compositions and physical properties that are responsible for the PAA's pulmonary toxicity and to design safer PAA materials, we synthesized four PAAs for the present study by chemically analyzing a PAA's crosslinker, performing a diameter measurement of a commercial PAA product, and then varying the PAA's crosslinker content. All the four synthesized PAAs were associated with inflammatory responses and fibrosis formation in rats through a single intratracheal administration of the PAAs, and the crosslinker content was revealed to be an important factor contributing to serious inflammation and long-lasting fibrosis in the lungs.