exotic dust incursions into central spain: implications for legislative controls on atmospheric...
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Atmospheric Environment 39 (2005) 6109–6120
www.elsevier.com/locate/atmosenv
Exotic dust incursions into central Spain: Implications forlegislative controls on atmospheric particulates
Teresa Morenoa,�, Xavier Querola, Andres Alastueya, Mar Vianaa, Wes Gibbonsb
aInstitute of Earth Sciences ‘‘Jaume Almera’’, CSIC, C/Lluis Sole i Sabarıs s/n, Barcelona 08028, SpainbAP 23075, Barcelona 08080, Spain
Received 25 January 2005; received in revised form 15 June 2005; accepted 27 June 2005
Abstract
The area of Castilla-La Mancha in central Spain is repeatedly visited by mineral dust incursions from the deserts of
NW Africa. Such exotic atmospheric intrusions raise background PM10 levels, making urban areas much more likely to
exceed daily limits of 50mgm�3 and become subject to fines under European environmental law. Data from a 3-year
(2001–2003) study of hourly PM10 values demonstrate that average background dust levels in remote sites rise from
6–8 mgm�3 when Atlantic-derived W/SW winds are blowing, to 24–7mgm�3 when African events take place. In four
Castilla-La Mancha towns, numbers of exceedence days (ED: when PM10450 mgm�3) per year averaged 31 in
Guadalajara (suburban site with annual daily PM10 average ADPM10 ¼ 27 mgm�3), 68 in Toledo (AD-
PM10 ¼ 38 mgm�3) and 139 in Albacete (ADPM10 ¼ 47 mgm�3; both urban sites), and 151 in Puertollano (industrial
urban site with ADPM10 ¼ 51 mgm�3). Thirty-four percent of ED occurred during African dust incursions, and current
law allows exclusion of such days from annual data (which also reduces the ADPM10 by 2–4mgm�3). Rather than
simply excluding such days, a more scientifically satisfactory approach would be to allow subtraction of the estimated
component of exotic background dust present daily at every urban monitoring station, and thus identify towns subject
to high levels of locally derived anthropogenic PM10. Such an approach reduces ADPM10 values by the same amount as
above (2–4mgm�3) if only African-derived PM10 values (as measured at remote background stations) are subtracted,
although SED shows a relative increase. If, however, an attempt is made to estimate and subtract the total amount of
exotic PM10 (i.e. not just African non-locally derived) at the four sites, this reduces the ADPM10 by 8–12 mgm�3, and
SED also drops significantly. Whichever approach is adopted, however, our data confirm that the legally allowable
number of ED is far more strict than the annual limit value. This inconsistency will make it especially difficult for many
southern European towns, with their abundant dry dust resuspension and regular incursions of African dust, to achieve
PM exceedence targets in 2005. We argue that further refinement of aerosol pollution law is necessary to ensure that
penalties for exceeding legally acceptable levels of atmospheric particulates are scientifically well founded and fair.
r 2005 Elsevier Ltd. All rights reserved.
Keywords: European environmental law; African dust; PM10; Central Spain
e front matter r 2005 Elsevier Ltd. All rights reserve
mosenv.2005.06.038
ing author. Tel.: +34934 095 410;
0 012.
ess: [email protected] (T. Moreno).
1. Introduction
The proven epidemiological link between enhanced
levels of breathable particulate matter (PM10: particles
with aerodynamic size o10mm) and poorer human
d.
ARTICLE IN PRESST. Moreno et al. / Atmospheric Environment 39 (2005) 6109–61206110
health (e.g. Pope et al., 1992; Dockery and Pope, 1996;
Hoek et al., 2002; Chen et al., 2004) has led directly to
environmental legislation designed to reduce anthropo-
genic dust. Such legislative controls are based on
measuring particle mass (mgm�3) on a 24 h basis, with
limits being set and exceedences punishable by fines.
Different countries have so far gone their own various
ways in defining acceptable limits of PM, ranging for
example for daily limit values from 50mgm�3 in the
European Union, 120 mgm�3 in New Zealand,
150 mgm�3 in American countries (Brazil, Costa Rica,
Mexico, USA), to 250 mgm�3 in some industrial areas of
Asia (Baldasano et al., 2003). Typically, both daily and
annual limits are set: 2005 limits within the European
Union (EU Directive 1999/30/EC) demand maximum
daily values of 50 mgm�3 (not to be exceeded more than
35 times a year) and mean annual values of 40 mgm�3.
By comparison, in the USA, the Environmental Protec-
tion Agency (EPA) introduced daily and mean annual
limits of 150 mgm�3 (PM10) and 50mgm�3 (PM10),
respectively, with no more than 4 days exceedences per
year. Some, but not all, countries have effected a further
refinement to their PM legislation by setting lower limits
for the finer, more respirable PM component (PM2.5:
particles with aerodynamic size o2.5mm), based on
studies that have reported an enhanced risk with PM2.5
(e.g. Schwartz and Meas, 2000; Anderson et al., 2001).
Thus, in 1997 EPA legislation in the USA was revised to
focus on PM2.5, setting limits for this finer fraction of
65mgm�3 (daily: with no more than 7 days exceedences)
and 15mgm�3 (annual: EPA, 2002). The importance of
such legislation is gaining in momentum, with countries
planning tighter future controls. In this context, by the
year 2010 the EU plans to demand the same daily limit
of 50 mgm�3, but with no more than 7 exceedences per
year, and with an annual value of only 20 mgm�3.
Similarly, the EU has recently (2004) recommended a
daily limit on PM2.5 of o35mgm�3 (with o37
exceedences/year).
There are at least four significant challenges asso-
ciated with this kind of pollution legislation. Firstly,
there is the current lack of agreement between countries
over what represents an acceptable PM-related health
risk, and, especially, the number of acceptable excee-
dences per year (e.g. McClellan, 2002). Secondly, an
emphasis on purely epidemiological arguments related
to PM mass versus health risk does not take into
account toxicological arguments concerning particle
composition, size, shape and corresponding variations
in potential bioreactivity of different PM samples (e.g.
Adamson et al., 1999, 2000; Dye et al., 2001; Ghio and
Devlin, 2001; Moreno et al., 2004). Thirdly, differing
monitoring stations within the same city may yield
different mass values for the same time period: great
care must be taken in locating representative sites for
data collection, and, most probably, the monitoring
stations will themselves need to be monitored by a
regulatory body. Finally, it is still not agreed as to how
the anthropogenic component of total measured PM
may be separated from a ‘‘natural’’ background
component. This latter point is bound to receive
increasing attention once PM-related fines begin to be
imposed on local governments. This paper is primarily
designed as a contribution to this question of anthro-
pogenic versus ‘‘natural’’, and locally derived versus far-
travelled, particulate matter using newly available
detailed data on air pollution levels in central Spain
over the period 2001–2003.
2. Saharan dust in Spain
EU Directive 1999/30/EC accepts that countries will
sometimes be subject to PM10 pollution events ascrib-
able to natural events defined as volcanic eruptions,
seismic activities, geothermal activities, wild-land fires,
high-wind events or the atmospheric re-suspension or
transport of natural particles from dry regions (EU
Directive article 2.15). Spain, already a relatively arid
European country and therefore one especially prone to
locally derived particle resuspension and high PM
values, is additionally vulnerable to frequent intrusions
of mineral dust plumes blown across from Africa
(Querol et al., 2001, 2002, 2004; Rodrıguez et al.,
2001, 2002; Viana et al., 2002; Escudero et al., 2005).
Although African dust outbreaks over central and
eastern Spain can occur throughout the year, they
are most common in the summer months, when
anticyclonic wind patterns and strong heating over
North Africa convect dust up to 5 km a.s.l. and
transport it northwards to Iberia (Prospero and
Carlson, 1980/1981; Viana et al., 2002; Escudero et al.,
2005). Fig. 1 illustrates an extreme example of one of
these summer African dust intrusion episodes, occurr-
ing in June 2002 when the weather was dominated
by an anticyclone centred over northern Morocco. The
impact of this major intrusion was recorded by
spectacularly high daily levels (60–80mgm�3) of PM10
in remote regional background EMEP stations (EMEP:
Cooperative Programme for the Monitoring and Eva-
luation of the Long Range Transmission of Air
Pollutants in Europe), with daily values of 4150mgm�3
being recorded in some urban and industrial monitoring
sites.
Newly available data allow examination of the impact
of such exotic dust intrusion events on the daily PM10
levels recorded in central Spain, particularly with respect
to the implications for possible future imposition
of air pollution fines. These data were obtained
during a 36-month study of daily pollution levels in
the Comunidad Autonoma of Castilla-La Mancha in
central Spain during 2001–2003 (Fig. 2a). The region is
ARTICLE IN PRESS
Fig. 1. Example of a summer African air mass intrusion over the Iberian peninsula in mid-June 2002. The NAAPS map shows dust
concentrations reaching maximum values in central Spain, and the NOAA backward trajectories indicate the arrival of air masses from
North Africa. During this desert dust intrusion daily PM10 levels at all stations in the Castilla-La Mancha region recorded an increase,
which, at one station, exceeded 150mgm�3.
T. Moreno et al. / Atmospheric Environment 39 (2005) 6109–6120 6111
mainly agricultural (although with some industrial
hotspots, notably Puertollano) and generally sparsely
populated, with the six largest towns being Toledo
(population 72,000; 529m a.s.l.), Guadalajara (69,000;
695m), Albacete (150,000; 686m), Puertollano (50,000;
709m), Ciudad Real (64,000; 650m) and Talavera
(61,000; 371m). Monitoring stations in the first four
of these towns (Fig. 2b) have revealed an overall
PM10 annual average of 41mgm�3 and many examples
of daily levels exceeding the legislative limit of
50mgm�3, especially during episodes of African dust
intrusion.
3. Geographical setting of monitoring stations
Castilla-La Mancha is geomorphologically distinctive
and well suited to a study of continental PM10
variations, being prone to stagnating intrabasinal
‘‘regional’’ pollution episodes as well as regularly
receiving air derived from Africa and the Atlantic. It
covers an area of around 80,000 km2, essentially forming
a high plateau surrounded by several mountainous
systems: the Central Range to the north and west, the
Iberian Ranges to the east and northeast, the Betic
Cordillera to the southeast, and the Sierra Morena and
ARTICLE IN PRESS
Fig. 2. Location and description of Castilla-La Mancha
monitoring stations. Note the two EMEP sites (Campisabalos
and Risco Llano) lie in extremely isolated positions and
represent background values with minimal local anthropogenic
contamination.
T. Moreno et al. / Atmospheric Environment 39 (2005) 6109–61206112
Montes de Toledo to the southwest and west (Fig. 2a).
Although a closed basin for much of Tertiary time,
Quaternary erosion opened it to the west and the
Atlantic Ocean, towards which it is now drained by the
Tajo River (Fig. 2a). This geomorphological setting
strongly influences annual air mass movement. Thus, the
Tajo river basin aids the transport of air masses from the
Atlantic into the peninsula, while the Central and
Iberian ranges inhibit the movement of air in from the
north and east.
The region is characterised by cold winters and hot
summers, with especially low rainfall in February, June,
July and August, and the wettest months being April,
May and October. Pollution levels are in part influenced
by these precipitation patterns, with highest average
PM10 values in Castilla-La Mancha consistently occur-
ring in June, July and August. Thus periods of low
rainfall in the region commonly coincide with times of
the year when African pollution episodes are most likely
to occur, reinforcing the likelihood of PM10 exceedences.
Ten sampling stations were selected from the Castilla-
La Mancha (Autonomous Government) and EMEP
remote station monitoring networks to study PM10
levels in central Spain. The stations were classified as
remote regional background (EMEP sites in Campisa-
balos and Risco Llano), suburban (Guadalajara,
Azuqueca), suburban/industrial (Puertollano Calle An-
cha, Puertollano Campo Futbol and Puertollano Barria-
da), urban (Toledo and Albacete) and urban/industrial
(Puertollano Instituto) (Fig. 2b). Hourly PM10 levels
were recorded throughout the 2001–2003 period with
automated instruments Beta Met One BAM1020, based
on the measurement of the absorption coefficients of
beta radiation in a glass fibre filter before and after the
collection of PM sample. Peaks corresponding to high
PM10 events in all stations were identified and analysed
to investigate the sources of the PM.
PM10 in Castilla-La Mancha towns will mostly
comprise a combination of traffic-related and indust-
rially derived technogenic aerosols, resuspended miner-
als from construction and agricultural activities and
natural wind transport, and a background component of
far-travelled anthropogenic particles and natural biolo-
gical and mineralogical materials. The background
component will be best measured at the sites least
contaminated by Spanish anthropogenic activity, repre-
sented here by the two EMEP stations at Campisabalos
and Risco Llano. Campisabalos is an extremely isolated
site situated high (1,360m) in the Central Range on the
far northeastern limit of Castilla-La Mancha (Fig. 2)
and over 65 km from the nearest sizeable town
(Guadalajara). Risco Llano is similarly isolated, lying
at 1241m in the Montes de Toledo, some 50 km SW of
Toledo (Fig. 2).
Table 1 shows dominant air mass transport directions
over the 3-year period 2001–2003, based on back-
trajectory interpretations using the Hysplit model
(Draxler and Rolph, 2003), with vertically modelled
transport back-trajectories being calculated for 5 days at
500, 1500 and 2500m a.s.l. Geographical sources for the
PM samples were apportioned into eight sectors,
depending on whether the air masses were from the
Atlantic (NW, W, SW), North Africa (NAF), the
Mediterranean (E), Northern Europe (NE, N) or
regional (REG). The latter was defined as including
all those pollution PM episodes produced when
ARTICLE IN PRESS
Table 1
Percentages of days in each year with different air mass source
origins according to back-trajectory studies
NW W SW NAF E NE N REG
2001 12 21 9 16 3 8 13 19
2002 16 30 5 15 7 8 12 7
2003 12 18 8 17 4 10 11 22
Average 13 23 7 16 5 8 12 16
NAF ¼ North African; REG ¼ regional events (without major
advective conditions).
EMEP background monitoring stations
0
10
20
30
40
50
60
70
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
µg/m
3
Campisábalos Risco Llano
1711131027689Risco Llano
17810924689Campisábalos
REGNNEENAFSWWNWSource (µg/m3)
Fig. 3. Average PM10 levels at the two isolated EMEP sites in
Castilla-La Mancha (Campisabalos and Risco Llano) during
the 3-year study period (2001–2003). The summer peaks occur
due to a combination of African air mass dust intrusions,
stagnating ‘‘regional’’ events during the development of low-
pressure systems over central-eastern Spain and the western
Mediterranean, and enhanced mineral dust resuspension under
semi-arid conditions. Average PM10 levels during different wind
directions show lowest values during Atlantic-derived advection
(NW, W, SW) and highest values during North African events
(NAF). Stagnating regional pollution events (REG), when
advection is reduced, also cause enhanced PM10 levels. The
slightly higher levels at Risco Llano during air mass transport
from the N and NE are attributed to anthropogenic pollution
plumes drifting SW and S from Toledo, Madrid, and Talavera.
T. Moreno et al. / Atmospheric Environment 39 (2005) 6109–6120 6113
slow-moving, stagnating masses of air were circulating
within central Spain and mixing with local airborne
contaminants.
The percentage of days annually during which winds
were sourcing from North Africa during the study
period was consistently around 16% (Table 1). This
compares with 19% NAF for southern Spain, 15%
NAF for eastern Spain and 5–8% NAF for northern
Spain (Querol et al., 2004; Escudero et al., 2005), these
figures reflecting the expected reach and influence of
African-derived dust as the plumes decline northwards.
The arrival of dust-laden air masses from the south is
most common during March (when western Saharan
and Sahel dust is preferentially transported across the
eastern Atlantic: Querol et al., 2002) and June (due to
the influence of North African anticyclones: for details
see Rodrıguez et al., 2001; Escudero et al., 2005).
Periods when regional air masses (REG) were
dominant in Castilla-La Mancha show the same 3-year
average as those for African-derived winds (16%)
although there was much more annual variation
(Table 1). These regional (or intrabasinal) air masses
tend to be more abundant in summer (May to
September), when the intense heat favours the develop-
ment of the Iberian thermal low over the Peninsula and
low barometric gradients over the Mediterranean (Mill-
an et al., 1997). The stagnating conditions of such a
scenario contrast with air masses derived from the west,
when Atlantic air moves over the Peninsula. The
prevalence of such western advection is due to atmo-
spheric circulation produced by low-pressure systems
moving into northwestern Europe from the north
central Atlantic, and the influence of the Azores
anticyclone which tends to dominate weather patterns
in Spain. The effect of these westerly winds is to cleanse
the atmosphere by advecting relatively unpolluted
oceanic-derived air across the Iberian landmass, com-
monly accompanied by precipitation.
The influence of wind direction on PM10 is tabulated
in Fig. 3, which shows monthly averages of back-
ground particulate levels at the EMEP remote sites
(Campisabalos and Risco Llano) over the 3-year
collection period, with levels rising to a maximum in
the summer months. Advective westerly and south-
westerly winds blowing across both sites predictably
bore the lowest amounts of PM10 (6–8mgm�3), with
both background sites recording remarkably similar
levels. Such averages are statistically highly robust,
having been based on over 25,000 hourly measurements
at each site.
4. Identifying and subtracting the exotic component
A total of 41 significantly polluting African dust
arrivals were detected during 2001–2003 (based on
Hysplit back-trajectory interpretations coupled with
information from TOMS–NASA and ICoD aerosol
index maps, and NASA SeaWIFS satellite images), a
pollution event in this context being defined as, when the
wind was blowing from Africa, daily PM10 value for the
combined average of all ten monitoring stations exceed-
ing 40 mgm�3. The average duration of these events was
3–4 days, and although their average frequency is just
over once a month, they were most frequent in the
summer (especially June) and least frequent from
October to December. During these episodes PM10
values commonly exceeded the daily limit value of
50mgm�3 in many of the monitoring sites.
ARTICLE IN PRESST. Moreno et al. / Atmospheric Environment 39 (2005) 6109–61206114
It is immediately obvious from Fig. 3 that PM10
masses from the two background sites during NAF
events are around three to four times heavier than those
collected when advective winds are blowing from the
Atlantic. The arrival of wind-blown African dust in the
Montes de Toledo and Central Range thus introduces
on average an additional daily respiratory burden of up
to 21 mgm�3. This may be compared to enhanced
pollution levels during ‘‘regional’’ events, when daily
PM10 levels rise on average up to 11 mgm�3 above
Atlantic advective background. Unlike the regional
episode PM10 burden, however, the extra dust received
during NAF events will be mostly ‘‘natural’’ mineral
dust rather than derived from anthropogenic sources
such as traffic and industry. The term ‘‘natural’’ is
placed in quotes here only to emphasise the fact that it
has been calculated that 50720% of total atmospheric
dust mass comes from anthropogenically disturbed soils
(Tegen and Fung, 1995). However, there is nothing that
Spain can do to avoid the influx of the African dust,
which is thus legitimately attributable to natural events
within the definition of EU Directive 1999/30/EC.
Table 2 records the average levels of PM10 at urban
monitoring stations in Guadalajara, Toledo, Albacete
and Puertollano, as well as the two EMEP stations of
Campisabalos and Risco Llano. The data selected from
Puertollano were from the most polluted (Puertollano
Instituto) of the four monitoring stations in this
industrial town, in order to illustrate the widest possible
range of PM values. It is clear that the data from
Albacete and Puertollano, with some annual PM10
averages reaching 50mgm�3 or more, reveal a severe
problem with PM pollution levels. A key question
therefore is how many of these exceedences can be
attributed specifically to the influx of African dust, and
to background exotic dust in general, and how much is
due to local anthropogenic pollution. In order to isolate
the ‘‘African’’ component of these data, Table 3 presents
the average number of days per year when PM10 levels
exceeded 50mgm�3 during North African events
(‘‘NAF’’ days). The same table shows the months of
the year when such days were recorded, illustrating the
importance of the ‘‘peak’’ months of March, June and
Table 2
Average PM10 annual levels (mgm�3) for the Castilla-La
Mancha monitoring stations in the 2001–2003 study period
Station 2001 2002 2003 Average
Campisabalos 14 10 11 12
Risco Llano 14 12 14 13
Guadalajara 27 26 28 27
Toledo 37 35 41 38
Albacete 44 48 50 47
Puertollano 49 50 53 51
July when 50% of these exceedences occurred. Over the
period 2001–2003 in the four urban sites, 34% of
exceedence days (when PM10450 mgm�3) occurred
when winds were bringing dust from Africa.
As from 2005 European towns recording annual PM10
averages of 440mgm�3 and/or more than 35 days when
PM10450 mgm�3 will be subject to fines. Legal protocol
will allow subtraction of ‘‘natural event’’ days so that in
central Spain we can estimate that around one third of
exceedence days will be declared non-anthropogenic and
thus escape financial sanction. However, in reality it is
highly unlikely that 100% of atmospheric PM10 during
NAF days will actually be mineral dust from Africa. A
source apportionment study of PM from a rural site in
NE Spain (Monagrega in the Ebro Basin: Rodrıguez
et al., 2002), for example, estimated that at this site only
around 50% of PM10 during NAF days is mineral dust,
a figure dropping to 25% for ‘‘non-African’’ days.
Moreover, the formation of chemical artefacts such as
gypsum, from chemical reactions between mineral air-
borne particles and ammonium sulphate in the atmo-
sphere, as has been reported in other dust intrusion
episodes (e.g. Kosa dust in China, Mori et al., 1998), will
also change the amount of directly African-derived
PM10.
The Monagrega site, however, although rural, is still
relatively contaminated, recording nearly twice the
annual PM10 average (22mgm�3: Rodrıguez et al.,
2002) of the background EMEP sites at Campisabalos
and Risco Llano. We view the two latter EMEP sites as
collecting particles that are far travelled, with minimal
local contamination, and thus essentially recording a
background exotic component of PM10 for all sites in
central Spain. If this view is valid, then subtracting such
background values from the four urban sites during
NAF days should provide a minimum estimate of more
locally derived pollution levels. Fig. 4 shows the effect of
such calculations, with the vertical arrows illustrating
the drop achieved by subtracting the values recorded at
Risco Llano (subtracting either daily results or annual
averages makes little difference: both lines are shown for
comparison). Using this approach the minimum number
of NAF exceedence days (450 mgm�3) remaining after
subtracting the African dust effect drops from 17 to 1 in
Guadalajara, 28 to 4 in Toledo, 38 to 14 in Albacete and
48 to 18 in Puertollano (Fig. 4). Fig. 5(i) (A and B)
shows the effect such subtractions have on overall
annual exceedence levels, reducing the average number
of 50mgm�3 exceedences from 31 to 15 (52%) in
Guadalajara, 68 to 44 (42%) in Toledo, 139 to 117
(15%) in Albacete and 151 to 123 (19%) in Puertollano.
Overall, this produces a reduction of 389 to 299 (23%) in
annual average number of exceedence days for the sum
of all four sites (Fig. 5(i)).
Fig. 5(i) also shows the effect of excluding all NAF
days (line C), as is currently legally allowable. This
ARTICLE IN PRESS
NAF exceedencessubtracting daily Risco Llano valuesubtracting 2001-2003 average (13µg/m
3) Risco Llano value
2001-2003
0
20
40
60
AlbaceteGuadalajara PuertollanoToledo
days
Fig. 4. Mean annual NAF exceedences ¼ number of days when
PM10 levels exceeded 50 mgm�3 during North African dust
intrusions over the 3-year study period (2001–2003) at
monitoring stations in four towns in Castilla-La Mancha
(Guadalajara, Toledo, Albacete, Puertollano). Solid line-
NAF exceedences�daily value at EMEP background site of
Risco Llano. Dashed line ¼ NAF exceedences�average PM10
value (averaged over 2001–2003) at EMEP background site of
Risco Llano.
Table 3
Number of average days per year when pollution levels were over 50 mgm�3 in the Castilla-La Mancha monitoring stations during days
when air masses had a NAF origin
Campisabalos Risco Llano Guadalajara Toledo Albacete Puertollano
Jan 0 0 0 0 1 2
Feb 0 0 1 2 3 3
Mar 0 1 2 4 8 7
Apr 0 0 0 0 1 1
May 0 0 0 1 1 3
Jun 1 2 8 10 10 12
Jul 0 0 1 3 5 7
Aug 0 0 2 3 3 5
Sep 0 0 0 2 2 3
Oct 0 0 0 1 1 2
Nov 0 0 1 1 0 1
Dec 0 0 0 1 2 1
Total 1 3 15 28 37 47
T. Moreno et al. / Atmospheric Environment 39 (2005) 6109–6120 6115
results in a reduction in annual average number of
exceedence days from 389 to 258 (34%) for the sum of
all four sites (Fig. 5(i) accompanying table). For
comparison, D and E on the same figure also shows
the result of subtracting PM10 values of the EMEP
background stations for every day of the year (not just
NAF days): D shows a subtraction (on non-NAF days)
of 6 mgm�3 (the Atlantic advective minimum: see Fig. 3),
whereas E subtracts the total daily value at Risco Llano.
This latter approach can be considered as providing the
most generous calculation from the point of view of
those threatened with pollution fines, as it assumes that
the entire PM burden collected at the EMEP control
sites on a given day is a combination of exotic ‘‘natural’’
and anthropogenic particles introduced beyond the
control of the area around the monitoring site. The
6mgm�3 subtraction drops the number of exceedence
days from 389 to 226 (42%), whereas subtracting the
Risco Llano daily values drops the annual average from
389 to 175 (55%) (Fig. 3). Taking either of these two
latter approaches (D or E) for the 3-year annual average
figures, under current legislation only Guadalajara and
Toledo fall below an average of 35 exceedences per year
rule and would not be subject to fines were the same
levels recorded in 2005.
With regard to the effect of these subtractions on
annual daily PM10 averages (ADPM10), Fig. 5(ii) shows
how there is no appreciable difference between either
subtracting values of the estimated amount of African
dust at Risco Llano, or taking the currently legally
acceptable approach of excluding all NAF days
altogether: both produce ADPM10 reductions of
2–4 mgm�3 (compare B and C in Fig. 5(ii) and the
accompanying table). However, if a more ambitious
attempt is made to estimate and subtract the back-
ground levels of exotic PM10, using the logic described
above for Fig 5(i) D and E, then appreciable drops in
ADPM10 are produced. Thus, under current legislation
only Guadalajara and Toledo would escape fines by not
exceeding legal ADPM10 limits, whereas subtracting a
minimum daily background value of 6mgm�3 from
curve B would have (just) made Albacete achieve legal
ADPM10 limits (Fig. 5(ii)D), and subtracting all daily
values from Risco Llano brings even Puertollano below
the current 40mgm�3 limit (Fig. 5(ii)E).
5. Discussion
This paper is primarily concerned with examining the
annual contribution of exotic dust to the daily levels of
ARTICLE IN PRESS
Average number of days per year when PM10>50µg/m3
2001-2003
Average daily PM10 (AD PM10)
2001-2003
DCBAAverage days
175226299389TOTAL
7597123151Puertollano
6286117139Albacete
29334468Toledo
9101531Guadalajara
Puertollano
Albacete
Toledo
Guadalajara
E
258
104
101
39
14
Total number of exceedences
Number after subtracting from A all daily
values in rural station (Risco Llano)
Drop in exceedences after subtracting African
dust background (Risco Llano)
Number after subtracting from B minimum
values (6µg/m3 ) in rural station (Risco Llano)
in non-NAF days
A:
B:
D:
E:
Drop when excluding all African dust intrusion
(NAF) days
C:
DCBA
39424751
37394447
26293438
17192427
E
47
44
35
25
Average PM10
Average daily PM10 (AD PM10) 2001-2003
ADPM10 after subtracting from A all daily
values in rural station (Risco Llano)
ADPM10 after subtracting African dust
background (Risco Llano)
ADPM10 after subtracting from B minimum
values (6µg/m3) in rural station (Risco Llano)
in non-NAF days
A:
B:
D:
E:
ADPM10 after excluding PM10 values during
all African dust intrusion (NAF) days
C:
10
20
30
40
50
60
A
B-C
DE
PM
10da
ys
0
20
40
60
80
100
120
140
160
Guadalajara Toledo Albacete Puertollano
Guadalajara Toledo Albacete Puertollano
A
B
CD
E
(i)
(ii)
Fig. 5. (i) Number of exceedence days during the 3-year study period (2001–2003) at monitoring stations in four towns in Castilla-
La Mancha: A ¼ mean annual number of exceedence days (PM10450mgm�3). B ¼ amount of reduction in numbers of exceedence
days (PM10450mgm�3) after subtracting EMEP background values (Risco Llano) during North African dust intrusions (NAF days:
see Fig. 4). C ¼ drop in exceedence days after subtracting all NAF days from A, as allowable by current European law. D ¼ drop in
exceedence days (PM10450mgm�3) after subtracting from B an Atlantic advective background value of 6 mgm�3 (see text) for non-
NAF days. E ¼ drop in exceedence days (PM10450 mgm�3) after subtracting EMEP background values for Risco Llano from A for
every day of the year. (ii) Average daily PM10 for the same period at the same stations: A ¼ average daily PM10 (AD PM10) 2001–2003.
B ¼ ADPM10 after subtracting African dust background (Risco Llano). C ¼ ADPM10 after excluding PM10 values during all African
dust intrusion (NAF) days. D ¼ ADPM10 after subtracting from B minimum values (6mgm�3) in rural station (Risco Llano) in non-
NAF days. E ¼ ADPM10 after subtracting from A all daily values in rural station (Risco Llano).
T. Moreno et al. / Atmospheric Environment 39 (2005) 6109–61206116
PM10 in the main towns of Castilla-La Mancha, as a
case study to illustrate potential problems associated
with the implementation of PM10-related pollution fines
in Spain and elsewhere in the world. In this context, we
concentrate on data from Toledo, Guadalajara, Alba-
cete and Puertollano, and compare these with the two
remote EMEP stations of Campisabalos and Risco
Llano (Fig. 2). We propose that the values obtained over
3 years from the EMEP stations, based on over 50,000
hourly measurements, represent the background levels
of far-travelled PM10 to which Castilla-La Mancha is
subjected. Subtracting such data from urban records
identifies which towns are subject to high levels of
locally derived anthropogenic PM10 and therefore
ARTICLE IN PRESST. Moreno et al. / Atmospheric Environment 39 (2005) 6109–6120 6117
should be most vulnerable to European pollution fines
in 2005. This is a more refined approach than that
required by current legislation, which allows Castilla-La
Mancha to delete wholesale around one third of
exceedence days, these being identified as natural events
due to African dust incursions. We argue that, rather
than simply delete all ‘‘African’’ days, it is scientifically
more satisfactory to identify and delete an exotic
background value derived from an appropriately sited
EMEP station, so that D or E in Fig. 5 more fairly
represent the amount of locally derived anthropogenic
PM in the four towns studied. If towns are to be fined
for their anthropogenic pollution levels, they need to be
shown that such levels are indeed locally derived so that
implementation of PM-reduction measures will achieve
positive financial results as well as improve population
health.
However, there remains a problem over what
constitutes a scientifically well-founded annual excee-
dence allowance. Fig. 6a plots the number of average
daily exceedences for 2001–2003 at the four urban sites
and at sites in several European cities for comparison
(data from AirBase, 2003) against annual average PM10
masses and illustrates that under current European law
and pollution levels in the studied area only Guadalajara
is likely to escape pollution fines in 2005 (pale shaded
rectangle), similar to the sites shown for Paris, Dublin,
Copenhagen, Berlin and London. As already empha-
sised by Querol et al. (2004), an important point
revealed by data such as those in Fig. 6a is that there
is typically a good correlation between exceedences and
annual averages. Thus for the annual average of
40mgm�3 required by the EU, the appropriate number
of exceedences should be closer to 80–85 for these
stations rather than the 35 allowed by the current
legislation, in which case Toledo (and most of the other
European cities shown) would join Guadalajara as being
below reasonable exceedence limits. Focusing only on
the four Spanish towns, if the EMEP background PM10
during African dust days is subtracted (Fig. 6b:
equivalent to B on Fig. 5), once again only Guadalajara
escapes fines under current law. Toledo in Fig. 6b now
lies way below the predicted number of exceedences at
40mgm�3 but is still higher than 35. As previously
revealed by comparing B and C in Fig. 5(ii), the data
shown in 6b (EMEP background subtracted on NAF
days) are very similar to the current legal position
illustrated in 6c which simply expunges all NAF days.
The latter approach again brings Toledo close to (but
still above) current legal limits.
As with D and E in Fig. 5(ii), Figs. 6d and e take the
logic of subtracting EMEP values, used in 6b, two stages
further. Fig. 6d (equivalent to D in Fig. 5) removes
6mgm�3 from each non-NAF daily value (and the full
Risco Llano value during NAF days), a calculation
which just brings Toledo under current legal limits. The
logic behind such a subtraction is that there will always
be an uncontrollable exotic component to any daily PM
reading, and this far-travelled component is unlikely to
be less than background Atlantic advection values
at a remote EMEP station (6–8 mgm�3 at Risco Llano).
Fig. 6e (equivalent to E in Fig. 5) goes one step further
and removes the EMEP background values from all
daily urban readings. This latter subtraction reduces the
predicted number of annual exceedences (at 40mgm�3)
to around 75 days (Fig. 6d). If such an exceedence limit
was deemed fair and acceptable, then not only Albacete
but also Puertollano Institute would lie within permitted
PM10 limits. In extreme contrast, if the European
legislation for 2010 is applied as planned (daily
50mgm�3 with only 7 exceedences and annual values
of 20 mgm�3), then even after subtracting background
values, few if any towns, not only in Castilla-La Mancha
but in the EU as a whole, are likely to escape financial
sanction (2010 rectangle in Fig. 6).
Another important consideration concerns the siting
of monitoring stations within urban areas. The
2001–2003 survey in Castilla-La Mancha concentrated
four monitoring stations in Puertollano, a town with a
mining, petroleum and chemicals industry. The stations
were sited in the centre (Calle Ancha), north (Barriada),
east (Campo Futbol) and south of the town (Instituto).
Annual average PM10 loadings are shown in Table 4,
with the number of exceedence days (450 mgm�3) for
each station. There is clearly great variation between
stations: if European rules for 2005 were applied
retrospectively to these four sites in Puertollano, then
only Campo Futbol (in 2003) and Instituto (all years)
would be subject to fines for exceeding an annual
average of 40 mgm�3. In terms of number of day
exceedences per year, again whereas three of the sites
would escape fines some years (Calle Ancha in 2001 and
2002; Barriada in 2002 and 2003; Campo Futbol in
2001), the Instituto site would not. It is likely that
similar variations will exist in all towns and cities where
PM10 are being monitored, and thus the siting of
monitoring stations could lead to great discrepancies
between fines imposed on different communities.
In conclusion, our data from central Spain illustrate
that by using large data sets from EMEP background
control stations it is possible to obtain a reasonable
estimate for the amount of exotic aerosols entering a
region. In theory, by subtracting the background dust
burden, it should be possible to derive a realistic
estimate of remaining, more locally and anthropogeni-
cally derived PM10. We argue that such an approach is
more scientifically realistic than simply deleting all PM10
exceedence days when African-derived air masses are
transporting dust to Spain. Not all NAF exceedence
days in Puertollano, for example, will be solely, or even
dominantly, due to African silicate particles. However,
care needs to be taken in siting recording stations within
ARTICLE IN PRESS
140
x = 40 µg/m3
n = 35
0
20
40
60
80
100
120
10 20 30 40 50
(d)
PuertollanoAlbacete
ToledoGuadalajara
10 20 30 40 50
(e)
x = 40 µg/m3
n = 35
Albacete
Guadalajara Toledo
Puertollano
0
20
40
60
80
100
120
140
x = 40 µg/m3
n = 35
Albacete
Guadalajara
Toledo
Puertollano
0
20
40
60
80
100
120
140
10 20 30 40 50
(b)
0
20
40
60
80
100
120
140(c)
Albacete
Guadalajara Toledo
Puertollano
x = 40 µg/m3
n = 35
10 20 30 40 50
R2= 0.962 R2= 0.943
R2= 0.961 R2= 0.992
Exc
eede
nces
Annual average PM10 (µg/m3)
Albacete
Guadalajara
Puertollano
Toledo
BerlinZurich
Sofia
Madrid
Copenhagen
WienBrussels
Praha
Paris
Athens
Dublin
Amsterdam
Warsaw
Lisbon
Kocani
Ljubljana
Oslo
Stockholm
0
20
40
60
80
100
120
140
160
180
200
10 20 30 40 50 60 70
R2 = 0.9711
x = 40 µg/m3
n = 35
London
(a)
Fig. 6. Exceedence days (PM10450 mgm�3) plotted against average annual PM10 values. (a) Raw data averaged over the 3-year study
period (2001–2003) for the four Spanish locations and for 2003 in sites from several European cities (Airbase 2003 data). Shaded areas
show European legislative limits planned for 2005 (pale) and 2010 (dark): only Guadalajara, along with Paris, Dublin, Copenhagen,
Berlin and London, escape exceeding the 2005 limits, but all lie well above 2010 limits. Note that for the 2005 European limit of
40 mgm�3 the predicted number of exceedence days (450 mgm�3) is close to 80–85 rather than the 35 currently allowed by law. (b)
Result of subtracting EMEP background values for Risco Llano during North African dust intrusions (see line B in Fig. 5). (c) Result
of subtracting all NAF days from the raw data: Toledo still remains above current limits so that under EU legislation for 2005 only
Guadalajara would escape fines. (d) Subtracts from 6b an Atlantic advective background value of 6 mgm�3 for non-NAF days (see D in
Fig. 5), bringing Toledo to just within the limits of 2005 legislation. (e) Result of subtracting rural background values for Risco Llano
during every day of the year (see E in Fig. 5): all four towns now lie within the predicted number of exceedence days for an annual
average of 40mgm�3, although Albacete and Puerollano still lie way outside current legislative limits.
T. Moreno et al. / Atmospheric Environment 39 (2005) 6109–61206118
ARTICLE IN PRESS
Table 4
Average PM10 levels and days of exceedences (450 mgm�3) for four monitoring stations located in different places in Puertollano
Annual average PM10 (mgm�3) and %
available data
Exceedence (days)
Puertollano Calle Ancha
2001 35 (94%) 30
2002 22 (93%) 3
2003 39 (97%) 71
Puertollano Barriada
2001 27 (86%) 40
2002 34 (32%) 16
2003 34 (46%) 30
Puertollano Campo futbol
2001 26 (92%) 14
2002 38 (91%) 85
2003 42 (97%) 102
Puertollano Instituto
2001 49 (96%) 127
2002 50 (91%) 147
2003 53 (99%) 180
T. Moreno et al. / Atmospheric Environment 39 (2005) 6109–6120 6119
the urban and industrial environment so that realistic
estimates are obtained of average PM10 levels that
people are actually breathing. Clearer protocols and
transparent monitoring of the monitoring stations
themselves will be necessary to ensure fair application
of financial sanctions between towns, regions and
countries in Europe. Finally, our results for central
Spain indicate that current PM10 statutory limits are
unreasonably harsh. As Querol et al. (2004) have shown,
and this study further confirms, there is currently a
legislative mismatch between limits defined in terms of
mass averages and those based on numbers of day
exceedences. This inconsistency will make it very
difficult for many southern European towns, especially
with their abundant dry dust resuspension and regular
incursions of African dust, to achieve PM exceedence
targets in 2005. We therefore argue, based on the rapidly
growing body of new data on European air quality, that
further refinement of aerosol pollution law is necessary.
Article 11 of EU Directive 1999/30/EC states that
penalties for exceeding legally acceptable levels of
atmospheric particulates shall be effective, proportionate
and dissuasive. They should also be seen to be
scientifically well-founded and fair.
Acknowledgements
This study has been financially supported by the
Spanish Ministry of the Environment and by the
Ministry of Science and Technology (REN2001-0659-
C03-03 and CGL 2004-05984-C07-02/CLJ), and the
Ramon y Cajal research programme (TM). The authors
are indebted to the Department of the Environment of
the Castilla-La Mancha Government for their colla-
boration in the development of this study, and would
like to thank the NOAA–Air Research Laboratory
(Silver Spring, MD, USA), the Euro-Mediterranean
Centre on Insular Coastal Dynamics (ICoD), NASA/
Goddard Space Flight Center (Maryland, USA), NRL
(Monterey, USA) and the SeaWIFS Project (NASA) for
the valuable information supplied by the HYSPLIT
model, TOMS, ICoD and NAAPs maps, and the
satellite images, respectively. We also acknowledge the
European Topic Centre on Air and Climate Change for
providing the AirBase data from European Cities.
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