Download Assignement_19012017

WAT-E2150 / Individual assignment 19.1.2016
Assignment: Site-specific risk assessment
Description of the task
Determine the health risks at the site. Take into account possible sensitive receptors in your
calculation and all relevant exposure routes (considering land use and properties of the
contaminants involved). Document your results in a report (see instructions below).
Calculate the human health risks for your site by following a tiered approach, e.g.
1) conduct Tier 0 risk assessment. Tip: you can use the benchmarks given in the Finnish
“PIMA decree” (can be found in the MyCourses page)
2) conduct a Tier 1 RA using the Excel-based calculation tool, use a conservative
approach.
3) conduct a Tier 2 RA with the Crystal Ball software using the Monte Carlo simulation
technique. Fit your soil concentration data of each COPC in log normal- distribution
curve using Crystal Ball and replace the deterministic value with the distribution. Replace
the deterministic values of the parameters related to exposure calculations and
parameters describing soil properties with the statistical values (see instructions below).
NOTE! If you are considering different age groups in your RA, you need to run the calculation
separately for each age groups you want to study. The reason for this is that except the body
weight, the calculation tool uses the average values (i.e. values that cover both adult and
children) for the parameters describing the characteristics and behavior of human receptor (e.g.
skin area, soil ingestion, inhalation rate). Therefore, you need to change these values
MANUALLY. (see Exposure parameters at the page “Laskentaparametrit”)
Input data
Tier 1: deterministic RA:
1) Concentration data: Calculate the 95% UCLs (upper confidence limit) for the COPCs.
Instruction: use the function based on Student’s t-test (this assumes a normal
distribution)
2) Parameters describing hydrogeological conditions: use the site data
3) Climate-related parameters: use the default values given in the calculation tool
4) Contamination level: use site data
5) Parameters related to the building: use site data and default values (when site data is
missing)
6) Exposure parameters: replace the default values with the 95% UCL values based on the
recommendations given in the Canadian Exposure Factors Handbook. Tip: UCL = µ ±
2σ, where µ = mean value and σ = standard deviation
Tier 2: probabilistic RA:
1) Concentration data: use the log-normal distribution
2) Parameters describing soil properties: change the deterministic values of hydraulic
conductivity and soil porosity (in vadose zone) to distributions. Use the range (min-max)
Page 1
WAT-E2150 / Individual assignment 19.1.2016
given in Table 2 in the file Soil types_and_properties.pdf. Assume that the value
measured at the site is the most probable value (=> select triangular distribution).
3) Exposure parameters: use the Canadian data (Exposure Factors Handbook ) on the
statistics of exposure parameters (Table 5.2. 6.1., 7.2, 8.1., 9.2.). In the time of activity
(table 8.1., you can use the Total indoors and Total outdoors values and assume that the
time spent at home is 70 % of the total time). For all of these exposure parameters you
can use the combined values, i.e. values that combine females and males.
Reporting
Your report should include at least the following:
1. Description of the conceptual site model (CSM) for the formation of human health risks;
you are free to choose the format of the CSM
2. Exposure routes and receptors considered in the RA (you can also report these along
with the CSM) and justification for your selection
3. Short description of the RA procedure and methods
4. Description of the input parameters used in the calculations (both deterministic and
probabilistic RA), preferably in a table. NOTE: you only need to report those parameters
that deviate from the default values (mention that you used these) included in the
calculation tool
5. Reference values (i.e. ADIs, RfDs) that were used in the calculations
6. Results from your deterministic calculations
- exposure estimates and risks for each exposure route and for each COPC
- total exposure and risk
NOTE! If relevant, consider also risks through ingestion of drinking water. Tip: you can
either 1) compare the concentration in groundwater/well against quality criteria for
drinking water (e.g. WHO, Finnish quality guidelines by STM) OR 2) calculate the
ingestion of groundwater and add it to daily intake through other routes.
- groundwater transport of COPC(s) in time (if relevant)
7. Results from the probabilistic RA
- the percentile corresponding the deterministic risk estimate
- interpretation = description of the magnitude and probability of risks and their
acceptability, uncertainties involved, your conclusion (does the site require some risk
management actions, e.g. remediation)
Additionally, you can search data on alternative benchmarks (TDIs, RfDs, etc.) for determining
your risks to find out the effect of the reference value and any additional uncertainties potentially
involved in the assessment (and not addressed in the probabilistic RA). You should then
document these in your report. You are free to choose the format of presenting your main
results (exposure and risk estimates), for example graphically or in a table.
You will earn extra “points” of the exercise if you have some suggestions for
improving/complementing the calculation tool 
Page 2