He attached an article, "Navajo Coal Combustion and Respiratory Health Near Shiprock, New Mexico," published in a peer-reviewed journal, the Journal of Environmental and Public Health. Some extracts follow.

Indoor air pollution has been identiﬁed as a major risk factor for acute and chronic respiratory diseases throughout the world ... In twenty-ﬁve percent of homes surveyed [on the Navajo Nation reservation] coal was burned in stoves not designed for that fuel, and indoor air quality was frequently found to be of a level to raise concerns ...

The majority of those surveyed used an indoor stove for heating (105 of 137, 77%); the remainder had electrical or other heating units. One quarter (34 of 137, 25%) of those surveyed were burning coal in stoves that were not designed to operate at the higher temperatures at which coal burns as compared to wood, and many of the stoves had visible cracks or were poorly ventilated to the outside ... Most stoves had chimneys (106 of 117, 91%); however many chimneys had holes, cracks, and ﬁssures ...

We found that the respiratory disease burden (as measured by hospital admissions and outpatient visits to the NNMC for the seven disease/conditions noted) is increased in the winter as compared to summer (Figure 1), and yet the power plant emissions are greater in the summer than those in the winter ...

This report presents the ﬁrst systematic study of coal combustion's likely impacts on respiratory health in Shiprock area of the Navajo Nation. Over 130 homes in the Shiprock area were surveyed, and stoves in one-quarter of those homes were found to be inappropriate for coal combustion, even typical for most of the Reservation. The presence of two large coal-ﬁred power plants near Shiprock may contribute to that risk, but results from this study suggest that the risk could be reduced by making relatively simple and inexpensive changes to methods of home heating.