Monitoring of Atmospheric Concentrations
of Benzene in European Towns and Homes
MACBETH (Monitoring of Atmospheric
Concentration of Benzene in European Towns and Homes) is the project
LIFE 96 ENV/IT/070 co-financed by the European Commission within the Life
program.
The project is comprised among
the preparatory actions aimed at helping the application of common policies
and laws for environmental protection, with special concern to the safeguard
of human beings from atmospheric pollution. The aim was to provide the
European law-makers with the correlation between benzene urban pollution
level and citizen exposure, in view of the issuing of the Daughter Directive
that should regulate benzene urban levels within December the 31st 1999,
as foreseen by the 96/62/EC Framework Directive on air Quality.
Conceived and coordinated by
to the project took part:
Fixing a limit value to the air concentration of
benzene is a delicate concern, both because of the carcinogenity of the
compound itself and due to the relevant economical and social implications
of any limitation to the accetable level of pollution, being benzene dispersed
in ari almost only by automotive traffic.
Limiting its concentration makes it necessary to
face several problems: reduction of the private traffic, development and
differentiation of the public means of transportation, rearranging of the
urban road network, interventions on fuels composition and on motor designing,
etc.
once the socially acceptable exposure risk level is stated by a political decision, one can set a limit value of benzene concentration in urban air only if the relationship between personal exposure and urban pollution is known
The scientific international literature makes us
deem, although cautiously, that exposure and risk levels can be correlated
on a scientific basis.
Different authors come to similar conclusions about
myeloid leukaemia cases increment estimates among the population exposed
to benzene. Grounding on these findings, the World Healt Organization stated
risk level between 4.4 and 7.5 cases every million people exposed continuosly
to 1 mg·m-3.
All the scientific papers deal with "exposure",
not with environmental concentration: the two parameters are not coincident
and their ratio can be known only experimentally. Therefore, a crucial
question must be faced: if one decided, as an example, to accept the risk
criterion proposed by WHO considering as "socially acceptable" the risk
of 22 to 37 additional cases of leukaemia every million people, that is
equivalent to a concentration of 5 mg·m-3,
and this, as a consequence, was stated as the limit concentration for urban
air, would one be certain the actual risk level is just that expected of
22-37 more cases? The answer can be given only if one knows which is the
citizen' exposure level corresponding to a 5 mg·m-3
urban concentration.
to answer this question, for an entire year six European towns and a sample of their citizens and their homes have undergone environenmtal monitoring
Hundred sampling sites on average have been choosen
in each of the towns of Antwerp, Athens, Copenhagen, Murcia, Padova and
Rouen, distributed along the knots of a multi-scale grid drawn over the
town map.
The sampling sites have been divided among an 85%
of background sites, a 10% of hot spots and a 5% of periurban
sites.
The background sites are open spaces as squares
or parks or streets apart from the intense traffic. The hot spots
coincided with road crossings or roads with intense or slowed down traffic.
The periurban sites were choosen in peripheral areas with scarce
or very flowing traffic. The percentage distribution is based on the idea
that people spend their time, on average, in diffrent kinds of places more
or less with the same distribution.
For six times each sampling site has been uninterruptedly
monitored from Monday morning to Friday afternoon.
At the same time fifty volunteers have undergone
personal sampling for the same duration. The volunteers were non-smokers,
divided into exposed and not exposed people. Actually, any
citizen is exposed to benzene: the distinction is between people who, due
to the duties of their job, spend a lot of time in the streets, and people
who spend more time indoor, in schools or offices. In the first group policemen,
postmen, street sweepers, stall-holders, newpaper keepers, bus and taxi
drivers are comprised. The second group is composed of students, teachers
and clerks.
The personal and home monitorings have been carried
out by the same technique and for the same duration of the environmental
ones. The volunteers' movements within the town area have been cheked by
an individual diary, allowing linking exposure levels with the exposure
places.
