Do contaminants cause pollution? To what extent do you agree?

Contaminants in the atmosphere appear to have harmful effects on neurodevelopment and cognitive function. When Lilian Calderón-Garcidueñas discovered abundant hallmarks of Alzheimer’s disease in a batch of human brain samples a few years ago, she initially wasn’t sure what to make of it. The University of Montana neuropathologist had been studying the brains as part of her research on environmental effects on neural development, and this particular set of samples came from autopsy examinations carried out on people who had died suddenly in Mexico City, where she used to work as a researcher and physician. Although Calderón-Garcidueñas had collected much of the tissue herself while attending the autopsies in Mexico, the light-microscope slides she was analyzing had been prepared by her colleagues, so she was in the dark about what patient each sample came from. By the end of the project, she’d identified accumulations of the Alzheimer’s disease–associated proteins amyloid-ß and hyperphosphorylated tau in almost all of the 203 brains she studied. “When I started opening envelopes to see who [each sample] belonged to. . . I was devastated, ” she says. The people whose brains she’d been studying were not only adults, but teens and even children. The youngest was 11 months old. “My first thought was, ‘What am I going to do with this? What am I going to tell people? ’” she says. “I was not expecting such a devastating, extreme pathology. ” Despite her shock, Calderón-Garcidueñas had a reason to be on the lookout for signs of a disease usually associated with the elderly in these samples. For the last three decades, she’d been studying the health effects of Mexico City’s notoriously polluted air—a blight that earned the capital the dubious distinction of most polluted megacity on the planet from the United Nations in 1992. During that time, she’s discovered many links between exposure to air pollution and signs of neural damage in animals and humans. Although her findings are observational, and the pathology of proteins such as amyloid-ß is not fully understood, Calderón-Garcidueñas argues that air pollution is the most likely culprit behind the development of the abnormalities she saw in her postmortem samples—plus many other detrimental changes to the brains of Mexico City’s residents.