It also builds off several other studies that have accumulated over the last 2 decades. It even says that in the conclusion of the study re-linked here: https://www.sciencedirect.com/science/article/abs/pii/S0749379726003168?dgcid=author

CONCLUSIONS

Extant literature has demonstrated that even low levels of lead contribute to significant impairments across the life course.1 Associations between firearm use and blood lead concentrations have been well documented among adults.4 For children, evidence is accumulating that firearm-related lead exposure may be a serious public health problem, as even low-level exposures result in higher levels of externalizing and depressive symptoms and an increased risk of criminality and violent injury.3,32,

Here's a separate NIH survey study that concludes you should avoid eating, drinking, or smoking while shooting, and washing and changing clothes after. As well as other precautions that are more out of your control most of time: https://pmc.ncbi.nlm.nih.gov/articles/PMC5379568/

Prevention includes clothing changed after shooting, behavioural modifications such as banning of smoking and eating at firing ranges, improved ventilation systems and oversight of indoor ranges, and development of airflow systems at outdoor ranges. Eliminating lead dust risk at firing ranges requires primary prevention and using lead-free primers and lead-free bullets.