Analysis of a new Mexican database reveals that air-borne, suspended particulate emissions per employee by plants with 20 or less employees are significantly greater than by larger plants within the same manufacturing sector. From a second, new data set on manufacturing plants in Brazil, it is shown that industry in lower-income areas displays a higher concentration of the dirtiest industrial sectors and of smaller plants (which are dirtier). However, harm to humans from industrial air pollution in Brazil is found to be greater in higher-income areas and most of this harm derives from larger plants. This is not simply a reflection of the greater prevalence of manufacturing in urban areas, for the rising projections of human mortality among higher wage municipalities hold, even controlling for population density. Resolution of this apparent paradox hinges on the distinction between emission intensities and total emissions, the latter determining the level of harm, a distinction that has not always been made clear in the course of debate.