Methods
The study comprised two parts namely an ambient air quality
monitoring and a Human Health Risk Assessment (HHRA).
Ambient air quality monitoring
A TOPAS airborne particulate monitor (Sira MC 090158/00) was
used to measure the ambient PM10 concentrations to which the
population of eMbalenhle were exposed. The monitor was installed
at eMbalenhle Sasol Club, alongside the Department of
Environmental Affairs (DEA) monitoring station (GPS coordinates:
S26°33,039' and E29°04,747'). Ambient PM 10 concentrations were
monitored for one month during winter (August 2010) and one
month during summer (February 2011). DEA monitoring station
data were also extracted for the same periods as the TOPAS
instrument was installed for comparison purposes.
The particulate monitor was calibrated and maintained according to
the manufacturers specifications. The fibre filters were replaced
once after two weeks. Monitored data used to assess the health
risks posed by exposure to PM10 in the population of eMbalenhle
were compared with the South African National Ambient Air Quality
Standard (NAAQS) [4]. The PM10 concentrations were measured in
15 minutes intervals, the raw data output was divided by a
calibration factor of 2 and the 24-hour averages were calculated.
The monitored PM10 concentrations were compared with the NAAQS
which were originally set to protect human health.
Human Health Risk Assessment
HHRA is a useful tool to estimate human health risks posed by
exposure to a given environmental pollutant. HHRA have been
applied in previous studies in South Africa, for example to estimate
kerosene [5] and sulphur dioxide-related health risks [6]. However,
a HHRA on PM10 has never been conducted in eMbalenhle. The
HHRA framework applied in this study comprised four parts: hazard
identification, exposure assessment, dose-response assessment and
risk characterisation. The formal identification of PM 10 as a hazard
as well as the types of health risks that may occur as a result of
exposure to PM10 was done from existing literature.
Dose-response assessment, i.e. how an individual will react to a
particular exposure, was not performed in this study as the extent
of the work requires comprehensive screening and additional health
data presently not available in South Africa. Instead, the measured
levels of PM10 were compared with the NAAQS. This national
standard was therefore used as a benchmark value.
The information obtained during the hazard identification and the
exposure assessment was used to estimate the concentrations of
PM10 that are likely to cause significant health risks in humans. The
PM10 monitored data were used to estimate how the different levels
of exposure to PM10 can impact on the likelihood and severity of
health effects.
It was postulated that the population of eMbalenhle was exposed to
levels exceeding the NAAQS for PM10 that may have a negative
impact on their health. It was assumed that inhalation was the most
Page number not for citation purposes 3
important route of exposure (not ingestion or dermal contact) and
that people were exposed for 24 hours per day.
Two equations were used to characterise the risks posed by
exposure to PM10, namely; the United States Environmental
Protection Agency (USEPA) Exposure Factors Handbook and the EPA
Integrated Risk Information System (IRIS) equations [7]. The
magnitude, frequency and duration of exposure of the population of
eMbalenhle to PM10 were unknown, thus the default values based on
the USEPA equations were used. The South African 24-hour
PM10 NAAQS of 120 µg/m3 was used as a benchmark value.
The USEPA equation was used to calculate the Field Average Daily
Dose (FADD). In order to calculate the FADD, the average
concentrations (C) of P PM10 monitored in eMbalenhle in August
2010 and February 2011 were multiplied by the Inhalation Rate
(IR), Exposure Frequency (EF) and Exposure Duration (ED), and
then divided by the Body Weight (BW) multiplied by the Average
Time (AT).
FADD was calculated using the following equation:
FADD = C × IR × EF x ED/ BW × AT (Equation 1)
Where:
FADD is the dose the population of eMbalenhle may be exposed to
when inhaling PM10 concentrations measured at eMbalenhle in
August 2010 and February 2011, expressed in µg/kg/day.
C is the average value of the PM10 concentration in the atmosphere
expressed in µg/m3. IR is the amount of contaminated medium (air)
inhaled per unit time or event. It is expressed in m3/day.
EF (Exposure Frequency) which is 350 days, because it was
assumed that a person will leave the area for about two weeks per
year.
ED (Exposure Duration) expressed in years. For non-carcinogens
assumed to be one year. BW is the average body weight of the
receptor over the exposure period (kg). AT is the period over which
exposure is averaged (1 year = 365 days). For non- carcinogens the
AT equals ED (years) multiplied by 365 days [7].
The long-term inhalation rates for adults and children (including
infants) were presented as daily rates (m3/day). It was assumed
that the 95th percentile inhalation rates for long-term exposures for
infants, children and adults (males and females combined,
unadjusted for body weight) range from 9.2 m3/day for infants from
birth to 1 year, 16.6 m3/day for children aged 6 to 10 years to 21.4
m3/day for adults aged 31 to 40 years [7].
The Safe Average Daily Dose (SADD) was calculated as follows:
SADD = C × IR × ED/ BW × AT (Equation 2)
Where:
SADD is the dose that the population of eMbalenhle may be
exposed to without suffering negative health risks, expressed in
µg/kg/day. In this case the concentration C represents the South
African 24-h standard for PM10 expressed in µg/m3. The rest of the
formula is the same as described above.
The risks caused by exposure to PM10 in the population of
eMbalenhle were characterised in terms of the potential risk to
illness or symptoms in the exposed population. The information
developed in the previous three steps (hazard identification,
exposure assessment and dose-response assessment) was brought
together in the risk characterisation step to quantify the potential
health risks in the exposed population, expressed as a Hazard
Quotient (HQ).
The HQ was calculated using the following equation [7]:
HQ = FADD / SADD (Equation 3)
Where:
HQ is the Hazard Quotient (which is always unit less)
FADD is the Field Average Daily Dose calculated (in µg/kg/day)
SADD is the "safe" average daily dose calculated (in µg/kg/day)
Guidelines for interpreting HQ calculations are (Lemly, 1996):
HQ 10: hazard is high
All statistical analyses were performed in Microsoft Excel. Ethical
clearance was obtained for this study from the Tshwane University
of Technology Research Ethics Committee on the 14th March 2011
(Reference number: 2011/03/007).
Results
Measured results of PM10
The measured 24-hour average PM10 concentrations for winter
(August 2010) and summer (February 2011) using both the TOPAS
and DEA instruments are presented in Figure 1 and Figure 2,
respectively. The PM10 concentrations measured in August 2010
were generally higher than the PM10 concentrations measured in
February 2011. The 24-h average level for PM10 (August 2010) was
157.37 µg/m3 and the 24-h average NAAQS of 120 µg/m3 was
exceeded on most of the days.
Figure 2 illustrates the PM10 concentrations monitored with the
TOPAS and DEA instruments during February 2011. The particle
pollution reported was relatively low (24-h average 63.70 µg/m3),
which means that even if the population of eMbalenhle was exposed
to that average concentration of PM10, negative health impacts
would be unlikely, as concentrations were below the 24-hour
average NAAQS of 120 µg/m3, although some individuals may still
be sensitive to relatively low PM10 concentrations [8].
Figure 3 presents the concentrations of PM10 versus time of the
day. High concentrations of PM10 were reported in eMbalenhle
between 04:45 and 07:45 probably due to the fact that people were
burning domestic fuel to prepare for work and they also travelled
from different areas during these times, thus elevated vehicle
emission levels were present. Figure 3 reflects that between 9:45
and 16:45, the PM10 concentrations decreased because most
residents were at work, thus the need for energy for cooking and
space heating decreased. Between 17:45 and 21:45, the
PM10 concentrations increased because residents were home and
engaged in cooking and household activities requiring domestic fuel
use.
A comparison between the winter and summer data from the
TOPAS PM10 data and DEA PM10 data was made (Figure
4a andFigure 4b respectively). Although the monitoring equipment
were placed at the same site, monitoring the same pollutant (PM10)
and within the same period (August 2010 and February 2011), the
PM10 concentrations monitored with the TOPAS monitor were higher
(but following a similar pattern in most cases) than those monitored
by the DEA monitoring station. The reason could be that an error
occurred during sampling or that one of the instruments was not
calibrated appropriately. Generally, when the PM10 concentrations
monitored with the TOPAS monitor increased, the
PM10 concentrations monitored by DEA monitoring station also
increased and vice-versa. However, the DEA PM10 instrument
measured on average three times lower than the TOPAS instrument.
Hence, to determine the worst-case scenario risk estimates, the
TOPAS data were used for the HHRA.
Human health risk assessment in eMbalenhle
The PM10 concentrations monitored in eMbalenhle in August 2010
and February 2011 were applied in the USEPA HHRA model to
assess and characterise the potential health risks posed by the
community. The population of eMbalenhle was categorised into
three life-stage scenarios (infant, child and adult). The three lifestage scenarios were categorised based on the fact that infan
 
MethodsThe study comprised two parts namely an ambient air qualitymonitoring and a Human Health Risk Assessment (HHRA).Ambient air quality monitoringA TOPAS airborne particulate monitor (Sira MC 090158/00) wasused to measure the ambient PM10 concentrations to which thepopulation of eMbalenhle were exposed. The monitor was installedat eMbalenhle Sasol Club, alongside the Department ofEnvironmental Affairs (DEA) monitoring station (GPS coordinates:S26°33,039' and E29°04,747'). Ambient PM 10 concentrations weremonitored for one month during winter (August 2010) and onemonth during summer (February 2011). DEA monitoring stationdata were also extracted for the same periods as the TOPASinstrument was installed for comparison purposes.The particulate monitor was calibrated and maintained according tothe manufacturers specifications. The fibre filters were replacedonce after two weeks. Monitored data used to assess the healthrisks posed by exposure to PM10 in the population of eMbalenhlewere compared with the South African National Ambient Air QualityStandard (NAAQS) [4]. The PM10 concentrations were measured in15 minutes intervals, the raw data output was divided by acalibration factor of 2 and the 24-hour averages were calculated.The monitored PM10 concentrations were compared with the NAAQSwhich were originally set to protect human health.Human Health Risk AssessmentHHRA is a useful tool to estimate human health risks posed byexposure to a given environmental pollutant. HHRA have beenapplied in previous studies in South Africa, for example to estimatekerosene [5] and sulphur dioxide-related health risks [6]. However,a HHRA on PM10 has never been conducted in eMbalenhle. TheHHRA framework applied in this study comprised four parts: hazardidentification, exposure assessment, dose-response assessment andrisk characterisation. The formal identification of PM 10 as a hazardas well as the types of health risks that may occur as a result ofexposure to PM10 was done from existing literature.Dose-response assessment, i.e. how an individual will react to aparticular exposure, was not performed in this study as the extentof the work requires comprehensive screening and additional healthdata presently not available in South Africa. Instead, the measuredlevels of PM10 were compared with the NAAQS. This nationalstandard was therefore used as a benchmark value.The information obtained during the hazard identification and theexposure assessment was used to estimate the concentrations ofPM10 that are likely to cause significant health risks in humans. ThePM10 monitored data were used to estimate how the different levelsof exposure to PM10 can impact on the likelihood and severity ofhealth effects.It was postulated that the population of eMbalenhle was exposed tolevels exceeding the NAAQS for PM10 that may have a negativeimpact on their health. It was assumed that inhalation was the mostPage number not for citation purposes 3important route of exposure (not ingestion or dermal contact) andthat people were exposed for 24 hours per day.Two equations were used to characterise the risks posed byexposure to PM10, namely; the United States EnvironmentalProtection Agency (USEPA) Exposure Factors Handbook and the EPAIntegrated Risk Information System (IRIS) equations [7]. Themagnitude, frequency and duration of exposure of the population ofeMbalenhle to PM10 were unknown, thus the default values based onthe USEPA equations were used. The South African 24-hourPM10 NAAQS of 120 µg/m3 was used as a benchmark value.The USEPA equation was used to calculate the Field Average DailyDose (FADD). In order to calculate the FADD, the averageconcentrations (C) of P PM10 monitored in eMbalenhle in August2010 and February 2011 were multiplied by the Inhalation Rate(IR), Exposure Frequency (EF) and Exposure Duration (ED), andthen divided by the Body Weight (BW) multiplied by the AverageTime (AT).FADD was calculated using the following equation:FADD = C × IR × EF x ED/ BW × AT (Equation 1)Where:FADD is the dose the population of eMbalenhle may be exposed towhen inhaling PM10 concentrations measured at eMbalenhle inAugust 2010 and February 2011, expressed in µg/kg/day.C is the average value of the PM10 concentration in the atmosphereexpressed in µg/m3. IR is the amount of contaminated medium (air)inhaled per unit time or event. It is expressed in m3/day.EF (Exposure Frequency) which is 350 days, because it wasassumed that a person will leave the area for about two weeks peryear.ED (Exposure Duration) expressed in years. For non-carcinogensassumed to be one year. BW is the average body weight of thereceptor over the exposure period (kg). AT is the period over whichexposure is averaged (1 year = 365 days). For non- carcinogens theAT equals ED (years) multiplied by 365 days [7].The long-term inhalation rates for adults and children (includinginfants) were presented as daily rates (m3/day). It was assumedthat the 95th percentile inhalation rates for long-term exposures forinfants, children and adults (males and females combined,unadjusted for body weight) range from 9.2 m3/day for infants frombirth to 1 year, 16.6 m3/day for children aged 6 to 10 years to 21.4m3/day for adults aged 31 to 40 years [7].The Safe Average Daily Dose (SADD) was calculated as follows:SADD = C × IR × ED/ BW × AT (Equation 2)Where:SADD is the dose that the population of eMbalenhle may beexposed to without suffering negative health risks, expressed inµg/kg/day. In this case the concentration C represents the SouthAfrican 24-h standard for PM10 expressed in µg/m3. The rest of theformula is the same as described above.The risks caused by exposure to PM10 in the population ofeMbalenhle were characterised in terms of the potential risk toillness or symptoms in the exposed population. The informationdeveloped in the previous three steps (hazard identification,exposure assessment and dose-response assessment) was broughttogether in the risk characterisation step to quantify the potentialhealth risks in the exposed population, expressed as a HazardQuotient (HQ).The HQ was calculated using the following equation [7]:HQ = FADD / SADD (Equation 3)Where:HQ is the Hazard Quotient (which is always unit less)FADD is the Field Average Daily Dose calculated (in µg/kg/day)SADD is the "safe" average daily dose calculated (in µg/kg/day)Guidelines for interpreting HQ calculations are (Lemly, 1996):HQ <0.1: no hazard exists;Page number not for citation purposes 4HQ 0.1-1.0: the hazard is low;HQ 1.1-10: the hazard is moderate; andHQ >10: hazard is highAll statistical analyses were performed in Microsoft Excel. Ethicalclearance was obtained for this study from the Tshwane Universityof Technology Research Ethics Committee on the 14th March 2011(Reference number: 2011/03/007).ResultsMeasured results of PM10The measured 24-hour average PM10 concentrations for winter(August 2010) and summer (February 2011) using both the TOPASand DEA instruments are presented in Figure 1 and Figure 2,respectively. The PM10 concentrations measured in August 2010were generally higher than the PM10 concentrations measured inFebruary 2011. The 24-h average level for PM10 (August 2010) was
157.37 µg/m3 and the 24-h average NAAQS of 120 µg/m3 was
exceeded on most of the days.
Figure 2 illustrates the PM10 concentrations monitored with the
TOPAS and DEA instruments during February 2011. The particle
pollution reported was relatively low (24-h average 63.70 µg/m3),
which means that even if the population of eMbalenhle was exposed
to that average concentration of PM10, negative health impacts
would be unlikely, as concentrations were below the 24-hour
average NAAQS of 120 µg/m3, although some individuals may still
be sensitive to relatively low PM10 concentrations [8].
Figure 3 presents the concentrations of PM10 versus time of the
day. High concentrations of PM10 were reported in eMbalenhle
between 04:45 and 07:45 probably due to the fact that people were
burning domestic fuel to prepare for work and they also travelled
from different areas during these times, thus elevated vehicle
emission levels were present. Figure 3 reflects that between 9:45
and 16:45, the PM10 concentrations decreased because most
residents were at work, thus the need for energy for cooking and
space heating decreased. Between 17:45 and 21:45, the
PM10 concentrations increased because residents were home and
engaged in cooking and household activities requiring domestic fuel
use.
A comparison between the winter and summer data from the
TOPAS PM10 data and DEA PM10 data was made (Figure
4a andFigure 4b respectively). Although the monitoring equipment
were placed at the same site, monitoring the same pollutant (PM10)
and within the same period (August 2010 and February 2011), the
PM10 concentrations monitored with the TOPAS monitor were higher
(but following a similar pattern in most cases) than those monitored
by the DEA monitoring station. The reason could be that an error
occurred during sampling or that one of the instruments was not
calibrated appropriately. Generally, when the PM10 concentrations
monitored with the TOPAS monitor increased, the
PM10 concentrations monitored by DEA monitoring station also
increased and vice-versa. However, the DEA PM10 instrument
measured on average three times lower than the TOPAS instrument.
Hence, to determine the worst-case scenario risk estimates, the
TOPAS data were used for the HHRA.
Human health risk assessment in eMbalenhle
The PM10 concentrations monitored in eMbalenhle in August 2010
and February 2011 were applied in the USEPA HHRA model to
assess and characterise the potential health risks posed by the
community. The population of eMbalenhle was categorised into
three life-stage scenarios (infant, child and adult). The three lifestage scenarios were categorised based on the fact that infan
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