Research by Nkomo on the relationship between lead exposure and crime in South Africa provides evidence that the lead-crime phenomenon is not limited to developed countries or caused by confounding variables localized to those areas. South Africa continues to experience lead exposure through traditional medicine and ammunition. In Nkomo's sample, the median blood lead level (BLL) was 5.6 μg/dL ($p < 0.001$). The study found that blood lead levels were significantly associated with physical violence ($p < 0.0001$). Specifically, BLLs between 5 and 9.99 μg/dL were associated with physical violence ($p = 0.03$), and BLLs $\geq 10$ μg/dL were associated with both physical violence and fighting ($p = 0.02$ and $p = 0.01$, respectively).