Housing affordability and security remain critical barriers to sustainable urban development. In 2024, about 1.16 billion urban residents – almost one in four – lived in slums or informal settlements, lacking access to safe water, sanitation, secure housing or adequate living space. Although the share of people in these conditions has slightly declined in some regions since 2015, rapid urban population growth has continued to drive up the total number of people affected, especially in sub‑Saharan Africa and parts of Asia. Yet progress is possible. In parts of Central and Southern Asia, slum-upgrading programmes, which improve housing conditions, connect residents to basic services and provide legal security over their homes, have contributed to measurable gains.

However, structural challenges – including barriers to affordable housing, insecure land tenure and limited urban planning capacity – continue to hold back broader progress. Without urgent, coordinated action, current projections suggest the global slum population could exceed 1.2 billion by 2030. Reversing course will require stronger housing policies, better data collection and reporting, and significantly more investment in inclusive urban development.

For decades, urban areas have consumed land faster than their populations have grown, straining infrastructure and displacing ecosystems. However, recent data signals a structural shift toward land-use efficiency. Based on 2025 data from 781 cities across 123 countries, urban land consumption and population growth rates have both declined and converged. Between 2015–2020 and 2020–2025, the annual land consumption rate fell from 1.24 to 0.83 per cent, while population growth declined from 1.07 to 0.81 per cent. While land consumption still marginally outpaces population growth, this narrowing trend demonstrates a measurable increase in global land-use efficiency. This positive trajectory is also backed by a small but gradual increase in urban densification rates.

That progress is encouraging, but land consumption still outpaces population growth, meaning cities continue to expand beyond what their populations strictly require. The cost of inefficient land use – especially in environmentally sensitive areas – is rising infrastructure expenses and increasing environmental degradation. More compact, efficient and data-informed urban planning will be needed to close the gap further.

Despite some improvements in global air quality – fine particulate matter fell from 34.4 µg/m³ in 2010 to 25.4 µg/m³ by 2020 before stalling at 26.1 µg/m³ in 2023 – regional progress has been uneven.

Central, Southern, Eastern and South-Eastern Asia saw steady declines through coordinated national action – though Central and Southern Asia still recorded the highest pollution levels globally. Meanwhile, Latin America and the Caribbean, Oceania, and Europe and Northern America saw progress plateau following initial gains. Sub-Saharan Africa and Northern Africa and Western Asia showed virtually no improvement.

In several regions, urban areas bore a disproportionate share of pollution, particularly in Central, Southern and Western Asia and Northern Africa and sub-Saharan Africa, where pollution was significantly higher in cities than in rural areas. By contrast, there was more even distribution across urban and rural settings in Europe and Northern America, Oceania and Latin America and the Caribbean.

Following the Second WHO Global Conference on Air Pollution and Health in March 2025, more than 100 countries pledged stronger air-quality standards, new funding to reduce air pollution and action to halve the health impacts of air pollution and reduce their contribution to climate change by 2040.