This World Health Organization fact sheet, “Ambient (outdoor) air pollution,” is included in PART 1: The Purposeful Investor (Call to Action: Our World & Our Future) because it documents the scale and equity dimensions of the crisis—99% of people live where WHO air-quality guidelines aren’t met, with an estimated 4.2 million premature deaths in 2019 (89% in low‑ and middle‑income countries)—and it sets out cross‑sectoral policy and investment solutions (clean energy, transport, waste management, urban planning) that align with the book’s argument that climate and nature harms are urgent human health and development issues requiring coordinated policy, regulatory and investment responses beyond individual action.