As a USA resident, the EPA is the best place to start when wondering about the emissions inventory of atmospheric pollutants or pollutant precursors that affect the National Ambient Air Quality Standards (e.g. Particulate Matter, Carbon Monoxide, Sulfur Dioxide, Lead, Nitrogen Oxides, Volatile Organic Compounds). The EPA compiles a comprehensive emissions inventory of all criteria pollutants at the county level which is available in the National Emissions Inventory (compiled once every 3 years). You can see the summary of your county at http://www.epa.gov/air/emissions/where.htm. As for the effects of atmospheric pollution, it is important to consider the lifetime of said pollutants in the atmosphere in order to put their environmental impacts into perspective. For instance, the air pollutants covered by the National Ambient Air Quality Standards have immediate health effects when high concentrations are breathed in regularly. Both animals and plants are adversely affected by these irritating and sometimes toxic chemicals, but these pollutants are also reactive and do not last long in the atmosphere unless they are constantly being replenished (e.g. daily traffic). Air quality also impacts critical nitrogen loads on ecosystems and possible production of acid rain.
If you are interested in Greenhouse Gases (e.g. methane, carbon dioxide, CFCs, nitrous oxide), the EPA has a separate site for those emissions since they are not part of the same regulatory framework http://www.epa.gov/climatechange/ghgemissions/ . Greenhouse gases typically do not cause adverse health effects for plants or animals on land. However, they have long-term radiative effects (e.g. the greenhouse effect) because they stay in the atmosphere for many years and trap infrared light. These long-term radiative effects are what can change climate and consequently land cover. Furthermore, most of the excess carbon is absorbed by the ocean, which creates carbonic acid. Increased acidity of the ocean causes severe problems for marine ecosystems.
The EPA states that in 2012 the CO2 equivalent GHG emissions for the USA by sector was:
Electricity production (32% of 2012 greenhouse gas emissions) - Electricity production generates the largest share of greenhouse gas emissions. Over 70% of our electricity comes from burning fossil fuels, mostly coal and natural gas.
Transportation (28% of 2012 greenhouse gas emissions) - Greenhouse gas emissions from transportation primarily come from burning fossil fuel for our cars, trucks, ships, trains, and planes. Over 90% of the fuel used for transportation is petroleum based, which includes gasoline and diesel.
Industry (20% of 2012 greenhouse gas emissions) - Greenhouse gas emissions from industry primarily come from burning fossil fuels for energy as well as greenhouse gas emissions from certain chemical reactions necessary to produce goods from raw materials.
Commercial and Residential (10% of 2012 greenhouse gas emissions) - Greenhouse gas emissions from businesses and homes arise primarily from fossil fuels burned for heat, the use of certain products that contain greenhouse gases, and the handling of waste.
Agriculture (10% of 2012 greenhouse gas emissions) - Greenhouse gas emissions from agriculture come from livestock such as cows, agricultural soils, and rice production.
Land Use and Forestry (offset of 15% of 2012 greenhouse gas emissions) - Land areas can act as a sink (absorbing CO2 from the atmosphere) or a source of greenhouse gas emissions. In the United States, since 1990, managed forests and other lands have absorbed more CO2 from the atmosphere than they emit.
If we consider GHGs on a global level (see Global Carbon Project http://www.globalcarbonproject.org/carbonbudget/index.htm ) we can see how each sector has impacted the atmospheric concentration of CO2 over the past 143 yrs.