Impax Funds Series Trust I is a registered investment company that offers exchange-traded funds (ETFs) focused on sustainable infrastructure investments; its flagship product is the Impax Global Infrastructure ETF (ticker: BLDX), which provides exposure to a diversified portfolio of global companies involved in infrastructure development, operations, and related services across sectors such as utilities, transportation, energy, and communications infrastructure. BLDX seeks to track the Impax Global Infrastructure Index, emphasizing companies with strong environmental, social, and governance (ESG) characteristics that contribute to long-term infrastructure resilience and growth, targeting institutional and retail investors interested in thematic equity strategies with inflation-hedging potential. The trust operates primarily in the United States, with BLDX investing globally across developed and emerging markets including North America, Europe, Asia-Pacific, and select emerging economies. Established under Impax Asset Management, with roots tracing to the firm's founding in 1998 and headquartered in London, UK, with key U.S. operations managed from California, the trust is part of Pax World Management LLC's broader platform following Impax's acquisition of Pax World in 2021, which expanded its sustainable investment offerings. Recent developments include the launch of BLDX in late 2023 as part of Impax's strategy to capitalize on post-pandemic infrastructure spending booms driven by U.S. Inflation Reduction Act initiatives and global energy transition policies; in 2025, Impax announced strategic enhancements to BLDX's index methodology to increase exposure to digital infrastructure and renewable energy assets amid rising demand, alongside a distribution partnership with leading ETF market makers to improve liquidity.