Lead pollution linked to IQ decline in ancient Rome
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A recent study published in the journal Proceedings of the National Academy of Sciences suggests that the Roman Empire experienced high levels of lead pollution, severe enough to potentially affect the health and cognitive abilities of its population. It sheds light on the environmental issues of ancient times, revealing that Romans were exposed to high levels of lead from extensive silver mining and smelting. The study estimates that this lead exposure could have resulted in a 2.5- to 3-point decrease in IQ levels across the Roman Empire. This research, notably, provides the earliest documented example of human-induced industrial pollution.
Source
J.R. McConnell, N.J. Chellman, A. Plach, S.M. Wensman, G. Plunkett, A. Stohl, N. Smith, B. Møllesøe Vinther, D. Dahl-Jensen, J.P. Steffensen, D. Fritzsche, S.O. Camara-Brugger, B.T. McDonald, A.I. Wilson, Pan-European atmospheric lead pollution, enhanced blood lead levels, and cognitive decline from Roman-era mining and smelting, Proc. Natl. Acad. Sci. U.S.A. 122 (3) e2419630121, https://doi.org/10.1073/pnas.2419630121 (2025).
Additional Reading
https://www.washingtonpost.com/world/2025/01/08/roman-empire-lead-pollution-iq-study/