Environmental Engineering Reference
In-Depth Information
in the world since the 1970s, and therefore its income data contained
ample variation over time, even within the states as growth had not been
equally rapid across all states. Third, income data overlapped between
the states. Fourth, the borders of most states were determined by ridges
that separated the major water basins and, to a certain extent, air basins.
Fifth, the states shared the same pollution policies, which varied across
pollutants.
According to Vincent's study, there was no evidence of EKCs for any of
the six income-pollution relationships in Malaysia. This result was incon-
sistent with previous research conducted using cross-country relationships.
With respect to population density, Vincent found that the net impact of
population density on TSP concentrations was positive and the interaction
term between population density and time was statistically signii cant but
negative. He attributed the positive impact to the various household activi-
ties, which were important sources of TSP concentrations, such as heating,
cooking, rubbish disposal and transportation. The negative interaction
term indicated a reduction in the per capita TSP concentrations due to the
pressure exerted through the enforcement of ef ective anti-pollution regula-
tions. For the water pollutants, and while holding income constant, Vincent
found that higher population densities were associated with worse water
quality for BOD and ammoniacal nitrogen, and better water quality for sus-
pended solids. He attributed this to the higher sewage discharge as a result
of higher population, in the case of BOD and ammoniacal nitrogen, and
the movement of people from rural to urban areas in the case of suspended
solids. The interaction term between population density and time was also
signii cant. It was negative in the case of BOD and ammoniacal nitrogen as
a result of the introduction of regulations to reduce BOD discharge and the
percentage of population without access to sanitary facilities. The interac-
tion term was positive for suspended solids indicating agriculture and set-
tlement movements to steeper and erosion-prone areas. In conclusion, the
author said that his i ndings did not mean that EKC did not exist anywhere,
but it meant that policy-makers should not assume that economic growth
was an automatic solution for the air and water pollution problems.
Kaufmann et al. (1998) attempted to explore the ef ects of income and
spatial intensity of economic activity on the atmospheric concentration
of SO
2
. They used a panel of international data for 23 countries with
observations between 1974 and 1989. Out of the 23 countries, 13 were
developed nations, seven were developing nations and three were centrally
planned economies. The data on SO
2
were obtained from the
United
Nations Statistical Yearbook
(1993) and GDP per capita and population
data were obtained from Summers and Heston (1993). The income data
were expressed in 1985 nominal US dollars. They used two variables to
