Combustion Engines Persist as Global Auto Industry Balances Efficiency, Electrification, and Health Impacts

Publication Date: July 19, 2025

Key Takeaway:
Internal‑combustion engine (ICE) vehicles remain the backbone of global transportation, emitting particulate matter (PM₂.₅) and nitrogen oxides (NOₓ) that carry confirmed health risks. While electric‑vehicle (EV) uptake is accelerating, vast ICE stocks and uneven adoption keep air‑pollution impacts high and fuel‑efficiency gains urgent.

Facts

Global ICE Prevalence:
By early 2025, the total global vehicle population reached about 1.64 billion units, of which over 90% rely on internal‑combustion engines. Under current trends, global light‑duty vehicle stock is projected to hit 2 billion by 2035.
U.S. Vehicle Sales Mix:
In 2023, battery‑electric vehicles (BEVs) made up roughly 7.6% of all light‑duty vehicle sales in the United States, with EV + plug‑in hybrids combined near 9%, leaving about 91% of sales to ICE and conventional hybrids.
Global Sales Mix:
Electric cars accounted for around 18% of new light‑duty vehicle sales worldwide in 2023, implying ICE + hybrid vehicles held approximately 82% of the market.
Mobile‑Source Mortality (U.S.):
Source‑apportionment modeling estimates mobile sources—predominantly ICE traffic—caused 21,000–55,000 premature deaths in 2011 (≈20% of air‑pollution mortality), declining to 13,000–37,000 deaths by 2025 (≈13%) thanks to cleaner fuels and stricter tailpipe standards.
Health Effects of PM₂.₅ & NOₓ:
- PM₂.₅: Ambient outdoor particulate pollution led to 4.2 million premature deaths globally in 2019; ICE exhaust contributes a substantial share of urban PM₂.₅.
- NO₂ & Ozone in the EU: In 2022, Europe saw an estimated 70,000 premature deaths from NO₂ exposure and 48,000 from ozone exposure.
Diesel Particulate (DPM) Carcinogenicity:
In 2012, the International Agency for Research on Cancer classified diesel engine exhaust—as a rich source of DPM—as carcinogenic to humans, with sufficient evidence linking it to lung cancer.
Leading EV Markets:
- Norway: Fully electric vehicles comprised 88.9% of new‑car registrations in 2024 (up from 82.4% in 2023).
- China: Battery‑electric cars alone made up about 24% of China’s 2023 new‑car sales, with plug‑in hybrids lifting total New Energy Vehicles to 35%.
Fuel‑Economy Standards:
The U.S. Corporate Average Fuel Economy standard requires a fleet average of 49 mpg by model year 2026, versus Japan’s fiscal‑year 2030 target of 25.4 km/L (≈60 mpg gasoline‑equivalent) for passenger cars.

Perspectives

Toyota Motor Corporation:
Emphasizes hybrid models—like the Prius Eco (58 mpg)—as a bridge solution that cuts urban tailpipe emissions and eases infrastructure demands while hundreds of millions of ICE vehicles remain in service.
China’s Ministry of Industry and Information Technology:
Points to China’s commanding share of EV production and low‑cost batteries (≈70% of global EV battery market) as key to reducing domestic and exported ICE‑related pollution.
U.S. Environmental Protection Agency:
Highlights mobile‑source emission reductions (from 20% to 13% of air‑pollution deaths between 2011 and 2025) via ultra‑low‑sulfur fuels and advanced catalytic converters, while urging continued vigilance in urban hot spots.
World Health Organization:
Warns that ambient air pollution—driven in large part by fossil‑fuel combustion—accounts for 4.2 million outdoor‑air premature deaths annually, and urges member states to accelerate electrification for public‑health protection.
American Lung Association:
Advocates for urban zero‑emission zones and tighter local controls, particularly in marginalized neighborhoods adjacent to busy highways where ICE exhaust exacerbates asthma and cardiopulmonary risks.
International Council on Clean Transportation (ICCT):
Argues that the health burden from ICE emissions—reflected in hundreds of thousands of premature deaths across major regions—justifies robust EV incentives, stringent fuel‑economy rules, and urban‑planning reforms to shift transport toward zero emissions.

Considerations

Equity and Exposure: ICE pollution disproportionately impacts low‑income and minority communities situated near major roadways, intensifying environmental‑justice concerns.
Intermediate Mitigation: Advances in diesel particulate filters (DPFs) and next‑generation catalytic systems can cut tailpipe PM₂.₅ and NOₓ significantly, but non‑tailpipe sources (tire/brake wear, road dust) will remain.
Grid & Lifecycle Impacts: Rapid electrification, coupled with decarbonized power grids, offers the only path to nearly eliminate operational ICE health impacts—but lifecycle emissions and raw‑material sourcing for batteries warrant parallel scrutiny.
Infrastructure & Behavior: Building fast‑charging networks and deploying incentives is critical to sustain EV growth; in the near term, hybrids may deliver the greatest combined mileage and emissions benefits in regions with lagging EV uptake.
Policy Synergies: Coordinated policies—linking vehicle‑efficiency standards, clean‑fuel mandates, and urban planning (e.g., low‑emission zones)—can multiply benefits and smooth the transition.

Readers are encouraged to review the cited sources and form their own conclusions on the optimal mix of technologies and policies to safeguard both mobility and public health.