Vol. 1(2) SEP 2011 - SAVAP International

Academic Research International
ISSN: 2223-9553
Volume 1, Issue 2, September 2011
It should however be noted that Selden and Song are very careful to point out reasons why
their forecasts should be treated with caution such as the fact that no attempt was made to
build into the analyses possible future changes in technology and their implications for
emissions.
A number of workers have found evidence that population growth causes an increase in
emissions. We start with one investigation which gives a good idea of the complexity of
interactions between population growth and other variables.
Cramer (1998) studied the relationship between population growth and air quality in
California in recent decades, attempting to disaggregate the relationship by 13 different
source categories and five pollutants. The source categories were:
Residential, Services, Commerce Natural Sources
Waste Burning
Passenger Vehicles
Solvent Use, Cleaning, Surfaces Trucks, Buses
Petroluem Production
Off-Road Vehicles
Industrial Processes
Other Transport
Agricultural Processes
Equipment
Miscellaneous Processes
The pollutants studied were reactive organic gases (ROG) and oxides of nitrogen (NO x ) (the
precursors of ozone), oxides of sulphur, carbon monoxide (CO), and particulate matter.
Population growth had been unusually rapid in California . In earlier decades this was mainly
due to inter-state migration. In recent decades it was due mainly to immigration from other
countries and relatively high fertility of some immigrant groups. While population growth
caused increases in some pollutants, “despite the population growth, air quality actually has
improved since the early 1980s due to aggressive regulatory efforts”.
The effects of population growth were found to vary considerably between pollution sources.
In general, population growth had a large, usually significant effect on emissions from source
categories like “Residential, Services, Commerce” and “On-road Vehicles”, sources with
consumption and commercial activities one would expect to be tied directly to population
growth. So population growth increased emissions for such source categories. In contrast,
population growth had insignificant effects on emissions from source categories related to
management and economic production such as “Waste Burning” or “Industrial Processes”.
The effect of population growth was found to vary between pollutants - a large effect on
ROG, NO x and CO, but little effect on small particles and SO x . While the effect of population
growth varied between pollutants, and for a base year of 1990, Cramer found that with
pollutants sensitive to population growth the overall impact of that growth had “an elasticity
of about 0.75 to 0.8; that is, a 10% increase in population produces an increase in emissions
of 7.5% to 8%”. They conclude that “this is a substantial impact, but..the elasticity is
considerably less than unity; a doubling of population does not double pollution...”. This
result stands in contrast to results with carbon dioxide we look at in some following work
It is clear that the relationship between population growth and pollution is a very complex
one. But as Cramer shows, the complexity does not stop with the factors analysed above. For
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