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San Francisco
Sophie Castillo
©2024 Keller and Heckman LLP

Sophia (Sophie) Castillo counsels domestic and international importers, distributors, national brands, private labels, institutional suppliers, family-owned food processing businesses, and retail grocers on compliance, litigation, and risk avoidance surrounding California’s Proposition 65, as well as other state and national laws related to chemicals and toxics. She advises clients involved in numerous industries across the entire supply chain, including food and beverage, cosmetics and personal care, dietary supplements, apparel, cookware, consumer products, and retail.

Sophie has an in-depth understanding of how exposure analysis provides the basis for California’s Proposition 65 and continues to stay abreast of the evolving regulation. She helps clients create compliant warning and labeling statements, conducts audits, and, if the need arises, will litigate and defend clients in Proposition 65 cases, including assisting with bounty-hunter claims. 

In addition to Proposition 65, Sophie counsels clients on other state laws, including California’s regulations related to PFAS and other emerging contaminants in products such as food packaging, cookware, and cosmetics. She also has experience working with chemical disclosure laws in the cosmetics and personal care products space. In her litigation practice, Sophie defends scientific and environmental law and toxic tort cases in litigation and regulatory proceedings and litigates complex multi-party Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) and contaminated property cases. Sophie also defends toxic tort matters involving chemicals in foods, beverages, consumer products, and pharmaceuticals.

Due to her vast knowledge of the legal landscape within these industries, Sophie is often invited to speak at industry conferences and author thought-leadership articles. Click here for a list of prior speaking engagements and publications. 

Prior to joining Keller and Heckman, Sophie was a litigation and Proposition 65 partner at a California-based law firm.

Representative Matters

  • Advised companies throughout the supply chain (European and U.S. manufacturers, importers, distributors, national brands, private label brands, family-owned food processing businesses, and retail stores) on warning mandates of California's Proposition 65 for chemicals in products, with focus on food and beverage, apparel, cooking appliance, and grocery industries
  • Defended, litigated, and settled Proposition 65 plaintiff claims and advised clients on associated indemnity obligations throughout the supply chain, including various industry-wide Proposition 65 matters
  • Provided compliance advice to U.S. and European companies regarding California chemical and recycling regulations, including PFAS/AB 1200, California's toxics in packaging regulations, and grocery recycling regulations
  • Represented client in multi-year natural resource damages (NRDA) regulatory process 
  • Litigated contaminated groundwater/soil cases pursuant to CERCLA and state law
  • Litigated toxic tort matter related to alleged cancer-causing chemicals in pharmaceutical product
  • Frequent presenter on Proposition 65 and related issues for trade groups, including the Specialty Foods Association, the Association of Food Industries, and the California Grocers Association


  • Food and Drug Law Institute (FDLI), California Programs Planning Committee
  • Prop. 65 Clearinghouse, Advisory Board Member
  • ProVisors Network Member
  • National Charity League, Inc.


  • The Best Lawyers in America®: Environmental Law, 2024
  • The Best Lawyers in America®: Litigation – Environmental, 2024
  • Super Lawyers, San Francisco, Environmental Litigation, 2024
  • JD Supra Readers’ Choice Awards, Food & Beverage, Top Author, 2021 – 2023
  • Attorney Intel, Top 50 Attorney of San Francisco, 2023
  • U.C. Hastings Pro Bono Attorney Honor Roll, U.C. Hastings Center for Gender and Refugee Studies, 2012
  • Hastings Law Journal, Articles Editor, 2004 – 2005
  • U.C. Hastings Moot Court Team, Roger Traynor Appellate Moot Court Competition, Second Place – Best Oral Argument, 2004


University of California, Los Angeles, B.A., 2002 cum laude
University of California, Hastings College of the Law, J.D., 2005