Air pollution is still a significant threat to public health globally. In the past decades, the lung and cardiovascular systems have been considered the principal organs affected by air pollution as evidenced by numerous epidemiological and experimental findings.
Recent evidence also suggests brain injuries arising from extended exposure to polluted air and the consequent neurodegenerative diseases and behavioral disorder symptoms.
In a previous recent study Calderón-Garcidueñas et al identified the existence of exogenous metal-rich and magnetic fine particles and Ti-rich nanorods in the human brain, and also showed evidence of entry via axonal transport, namely from the GI tract, as the key port of entry and subsequent transport to the brain.
Yu Qi et al recently published a study in which they investigated the intrusion and retention of exogenous fine particles into the brain using in vitro and in vivo models.
Particles found in the brain of those with Neurodegenerative conditions
For the study, the team examined the cerebrospinal fluid and blood of 25 patients with various mental disorders at a Chinese hospital and found different toxic fine particles in the cerebrospinal fluid of 32% of the participants as well as in the blood.
The team also examined samples from 26 healthy people and found particulate matter only in one individual.
The type of particles found by researchers were commonly found in air pollution, such as calcium-based particles, like calcite and aragonite, minerals used in construction materials, soil-treatment, and even in some pharmaceuticals. Other particles found, included iron and silicon.
To examine how the particles get into the brain, the researchers used a mice model and found that particles could traverse the oxygen-blood barrier to enter the bloodstream and then could cross the blood-brain barrier.
The study adds to the associations previously done between inhalation and particle transport and adds evidence on how air pollution can have detrimental effects even in the brain, possibly contributing to the generation of neurodegenerative conditions.
Yu Qi, et al. Passage of exogeneous fine particles from the lung into the brain in humans and animals. 2022. PNAS. https://doi.org/10.1073/pnas.2117083119