Chlor-Alkali Diaphragm

A chlor-alkali diaphragm is a porous barrier used inside industrial electrolytic cells that produce chlorine, sodium hydroxide, and hydrogen from salt brine. For most of the 20th century and into the 21st, these diaphragms were made primarily from chrysotile asbestos because the fibers resisted harsh chlorine and caustic conditions. Workers who manufactured, installed, replaced, or disposed of these diaphragms could inhale asbestos fibers during normal plant operations.

Origin

The chlor-alkali industry adopted asbestos diaphragm cells in the early 1900s, with the Hooker S-type cell (introduced by Hooker Chemical in the 1920s) becoming a dominant design in North America. Asbestos was chosen for its chemical resistance, and its use in this application continued long after asbestos was banned in most other products. The U.S. EPA did not finalize a ban on chrysotile diaphragms until the 2024 chrysotile rule, with phase-out periods extending years beyond.

Significance in Asbestos Context

Chlor-alkali plants are one of the last industrial settings in the United States where workers had ongoing, documented exposure to raw chrysotile asbestos decades after most other industries had transitioned away. For patients diagnosed with mesothelioma, lung cancer, or asbestosis who worked at chlorine plants — or in trades that serviced them (millwrights, pipefitters, electricians, laborers, contractors) — diaphragm work is a high-yield exposure source to document. Because diaphragms were periodically removed, reslurried, and reformed on cathodes, fiber release was not a one-time event but a recurring part of plant maintenance cycles. Defendants in these cases often argue that modern dust controls made exposures negligible; industrial hygiene records, OSHA citations, and co-worker testimony are central to rebutting that claim.

Example Sentence

His attorneys focused on the years he spent rebuilding chlor-alkali diaphragm cells at the Louisiana plant, because that work involved hands-on contact with raw chrysotile fibers well into the 2000s.

Related Terms

Chrysotile, Occupational Exposure, Bystander Exposure, Industrial Hygiene, Cumulative Dose, Friability

Notes

• If you or a family member worked at a chlorine, caustic soda, or PVC-feedstock plant (companies such as OxyChem, Olin, Westlake, PPG, Dow, Formosa, or the former Hooker Chemical), list every job title, unit, and date. Diaphragm cell rooms are a specific exposure zone worth identifying.
• Ask for and preserve any plant industrial hygiene records, air-monitoring data, MSDS/SDS sheets for diaphragm materials, and OSHA inspection reports; these documents often show measurable airborne fiber levels.
• Contractor and maintenance workers (millwrights, insulators, electricians, pipefitters) who entered cell rooms can have significant exposure even without being plant employees. Gather W-2s, union records, and project assignments.
• Tell your treating physician about chlor-alkali work specifically, not just "chemical plant work," so the occupational history in your medical record accurately reflects chrysotile exposure.
• The EPA's 2024 chrysotile rulemaking record contains industry admissions about ongoing diaphragm use and exposure potential. Your legal team can request these materials as part of case development.