Paul Crimmins is an environmental scientist and Certified Air Quality Practitioner with over 18 years’ experience in air quality and climate mitigation and regulation. His work spans industrial, construction and infrastructure, and energy sectors, with a strong focus on human health risk assessment and regulatory decision making. Paul has advised on hundreds of successful resource consent applications and compliance actions. Many of these cases required determining how best to assess risks to human health including what weighting to place on predicted off-site exposures and relevant ambient air quality assessment criteria. Paul’s experience provides a practitioner perspective on how the WHO AQGs are used by NZ regulators and environmental advisors in practice, where challenges arise, and how they influence regulatory outcomes.