ENVIRONMENTAL RISK ASSESSMENT OF WASTE DISPOSAL FACILITIES

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ENVIRONMENTAL RISK ASSESSMENT OF WASTE DISPOSAL
FACILITIES

• Arvind K Nema
• Department of Civil Engineering,
• Indian Institute of Technology, Delhi
• aknema_at_gmail.com

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Introduction

• Quantity of municipal solid waste (MSW) continues
  to grow in spite the efforts to reduce and
  recycle.
• Landfills play a significant role in the disposal
  of residual MSW in most developing countries.
• An important factor, however, is the lack of
  basic epidemiological data on the health impact
  of prevailing waste management practices that
  would motivate and drive the authorities to adopt
  safer management techniques.
• Little attention has been given on the health
  impacts of acute and chronic exposure due to MSW
  disposal facilities.

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Objective and Scope

• The objective of this study was to assess the
  ground level pollutant concentrations due to
  emissions from landfills and to estimate the
  associated human health risk.
• The scope of the work was to assess the
  incremental lifetime cancer risk of inhalation
  exposure to emissions from a landfill.
• Secondary data were used to estimate emission
  rate of pollutants from landfills.
• A case study of Okhla landfill site of New Delhi,
  India is presented to demonstrate the utility of
  the methodology.

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Risk Assessment Concepts

• Risk assessment is the quantification of the
  potential for adverse effects due to chemicals
  released into the environment.
• Risk the probability of adverse consequence x
  severity of consequence
• Risk is reported as a probability of occurrence,
  such as the chance of death per million or the
  lifetime cancer risk.
• Risk assessment also requires an evaluation of
  the routes of exposure, dose, duration and the
  sensitivity of the receptor.

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Risk Assessment Concepts

• Risk principles
• Steps in risk assessment
• Risk calculations

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Exposure Assessment

• Characterize Exposure Setting
• Physical Environment
• Potentially Exposed Populations

• Identify Exposure Pathways
• Chemical Source/Release
• Exposure Point
• Exposure Route

Quantify Exposure
Exposure Concentration
Intake Variables
Exposure
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• Estimation of Chemical Intakes
• Chronic Daily Intake (CDI)
• Daily Intake DI (mg/kg-day) C (mg/vol)
  Intake (vol/day) / body mass (kg)
• CDI DI averaged over exposure
• Lifetime average daily doseLADD DI averaged
  over 70 year lifetime
• Models for various exposure routes
• Lots of factors, exposures
• Typical or default values in databases

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• Estimation of chemical intakes example
• Air intake - on-site, commercial, adult
• lifetime 70 yrs
• body wt. 70 kg
• inhalation rate 20 m3/day (2.5 m3/hr x 8
  hr/day)
• concentration 0.2 mg/m3
• DI
• CDI
• LADD
• note absorbed vs. administered dose

• exposure duration 25 yrs
• frequency 250 days/yr

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Uncertainties

• Land use, ground water flow, characterization
• Parameter uncertainty and sensitivity
• Quantitative techniques for uncertainty and
  sensitivity
• Confidence intervals
• Monte-Carlo techniques
• Health affects, toxicity parameters

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• Dose-Response Curves - Carcinogens

95 upper confidence limit
extrapolation
Humanexposure
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• Dose levels (animal studies)
• NOEL no-observed effect level
• NOAEL no-observed-adverse effect level
• LOAEL lowest-observed-adverse effect level
• MTD maximum tolerated dose
• LD50 dose which kills 50 of population
• LC50 concentration which kills 50 of
  population must include time frame

Increasing dose
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• Reference dose
• is an estimate of the daily dose of a chemical
  that will avoid toxic effects other than cancer
• The animal dose (NOAEL, LOAEL) is adjusted by
  uncertainty factors (UF) to allow for differences
  in sensitivity to chemicals.
• Human data UF 10
• Animal data
• UF 100 (NOAEL), 1000 (LOAEL), 1000 (NOAEL, less
  data)

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• Reference dose (cont.)
• RfD NOAEL/UF
• 100 mg/kg-day / 100 1 mg/kg-day
• Use RfD to establish allowed concentrations
• allowed C RfD x body wt / daily intake 1
  mg/kg-day x 70 kg / 2 liters/day 35 mg/l

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• Dose-Response Curves (non-carcinogens)

Response
RfD
NOAEL
LOAEL
Dose (mg/kg-day)
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Example 1

• It is now 2011 and you, along with 400,000
  residents of your community, find that for the
  last 35 years they have been drinking water that
  contains the chemical CIXOT. Although no one knew
  that this chemical was toxic until recently, the
  water treatment plant monitored for this chemical
  along with the suite of regulated chemicals. The
  average concentration over the last 35 years has
  been 4.6 µg/L. The cancer potency slope factor
  (also known as the potency factor) is 13.1
  (mg/kg-day)-1. At this concentration of CIXOT,
  what would be the expected number of additional
  adult cancers in this community, using standard
  values for daily intake due to ingestion?

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Example 1
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Example 1 CDI
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Example 1
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Example 1
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Example 2

• Suppose residents residing along a lake release a
  continuous flow of the carcinogenic herbicide,
  MTX, into a local lake. At steady state
  conditions and complex mixing, the concentration
  of MTX in the lake is 334 µg/L in the lake. The
  lake does not serve as a drinking water supply
  but many people swim in the lake. Suppose this
  carcinogen has an absorption potency (slope)
  factor of 0.71 (mg/kg-day)-1. Assume that the
  dermal uptake from water (PC) is 9.0 x 10-6 m/h.
  Assume that the average person swims in the lake
  five times per week for seven months each year
  for fifty-five years. The average lifespan is
  seventy years. This "average" person spends 1.25
  hours in the lake each time he/she swims. The
  average available skin surface area is 1.89 m2.
  What is the absorbed dose in mg/kg-day?

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Example 2
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AD
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Risk Estimation Methodology
Landfill (historical data on waste quantity and
its characteristics)
Estimation of LFG (LandGEM model)
Emission rate
Emission factor
ISCST3 dispersion model
Meteorological data
Ground level concentration
Population data
Individual cancer risk
Population cancer risk
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Schematic Representation of Waste Disposal
Facility
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Accidental Fire in Waste Disposal Facilities

• Fires occurring at landfill sites across are an
  ongoing but complex problem.
• Landfill fires threaten the environment through
  toxic pollutants emitted into the air, water, and
  soil.
• These fires also pose a risk to landfill workers
  and nearby receptors.
• The degree of risk depends on the contents buried
  in the landfill, the geography of the landfill,
  and the nature of the fire.
• There can be great difficulty in the detection
  and extinguishment of landfill fires, which is
  compounded because these fires often smoulder for
  weeks under the surface of the landfill before
  being discovered.
• This study present paper aims to determine how
  various events are related and how they are
  linked to specific operational problems using
  logic diagrams like fault trees.

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Issues related to Landfill Fire

• Depending on the type of landfill and its
  contents, the smoke from a landfill fire may
  contain dangerous chemical compounds, which can
  cause respiratory disorders and other medical
  conditions.
• Even if the smoke is benign, it can still
  aggravate existing respiratory conditions and
  reduce visibility around the landfill.
• In addition, contrary to conventional thinking,
  the use of large amounts of water to suppress a
  landfill fire can actually make the fire worse by
  increasing the rate of aerobic decomposition,
  which increases the heat available inside the
  landfill.
• Further, runoff from suppression efforts can
  overwhelm a landfills leachate collection system
  and contaminate ground or surface water sources.

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Issues related to Landfill Fire..

• Fire may also compromise the structural integrity
  of a land-fill, posing a collapse hazard for
  personnel operating on the fire ground.
• Landfill fires fall into one of two categories,
  surface and underground fires.
• Depending on the type of landfill and type of
  fire, landfill fires can pose unique challenges
  to the landfill/ waste management industry and
  the fire service.

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Characteristics of Landfill fires

• Involve recently buried or un compacted refuse,
  situated on or close to the landfill surface in
  the aerobic decomposition layer.
• These fires can be intensified by landfill gas
  (methane), which may cause the fire to spread
  throughout the landfill.
• Generally burn at relatively low temperatures and
  are characterized by the emission of dense smoke
  and the products of incomplete combustion.
• The smoke includes irritating agents, such as
  organic acids and other compounds.
• When surface fires burn materials such as tires
  or plastics, the temperature in the burning zone
  can be quite high.
• Higher temperature fires can cause the breakdown
  of volatile compounds, which emit dense black
  smoke.

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Surface Fires

• Fires associated with landfill gas control or
  venting systems
• Fires caused by human error on the part of the
  landfill operators or users
• Fires caused by construction or maintenance work
• Spontaneous combustion of materials in the
  landfill
• Deliberate fires, which are used by the landfill
  operator to reduce the volume of waste

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Under Ground Fires

• The most common cause of underground landfill
  fires is an increase in bacterial activity which
  raises temperatures (aerobic decomposition).
• These so-called hot spots can come into contact
  with pockets of methane gas and result in a fire.
  
• This can cause a build up of the by products of
  combustion in confined areas such as landfill
  site buildings or surrounding homes, which adds
  an additional health hazard.
• Underground fires are often only detected by
  smoke emanating from some part of the landfill
  site or by the presence of CO in landfill gas.

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Fault Tree Analysis (FTA)

• A fault tree is a logic diagram that displays the
  inter-relationships between a potential critical
  event in a system and the reasons for, or causes
  of, this event.

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Fault tree for Surface fires
SURFACE FIRES
AND
Exposed combustible materials

Favourable weather conditions
Fire Sources
OR
OR
OR
Combustion of Materials
Hot Parts contact with waste
Windy conditions
High ambient temp
Partially covered waste
Flammables not covered
OR
OR
Reactions in waste and emission of gases
Burning loads from trucks
Human error or deliberate fires
Construction equipment
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Fault tree for Underground fires
UNDER GROUND FIRES
AND
Oxygen supply in buried waste
Heat Source
OR
OR
Air through soil cover
Overdrawing of Biogas from extraction wells
OR
Surface Fires
High Temp of the buried waste
Partially covered waste
Unsatisfactory waste compaction
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Unsatisfactory Waste Compaction
OR
Slopes are not compacted
Properties of Waste
OR
OR
Problem with steel wheel compactor
Human error
Water content to obtain min dry density of waste
(475 Kg/m3
Operator errors
OR
OR
Wt. of compactor not match with waste
Compactor teeth are worn out
Unsatisfactory no. of passes (lt3 -4) over waste
Waste mixture during compaction
Ht of waste layers(gt5m) during compaction
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Results of fault tree analysis

• Probabilities of occurrence
• Surface fires 4.64E-03
• Underground fires 5.91E-03
• According to probability scale table, the fires
  are occasional.

Probability Scale
1 in 10 Frequent
1 in 100 Probable
1 in 1000 Occasional
1 in 10000 Remote
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Estimated Pollutant Emission Rate
Compound Emission Rate (g/s-m2)
Compound Emission Rate (g/s-m2)
1,1-Dichloroethene 1.05E-08
Benzene 8.06E-08
Chloroform 1.93E-09
Tetrachloroethylene 3.34E-07
Trichloroethylene 2.00E-07
Vinyl chloride 2.48E-07
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Risk Estimation

• Incremental lifetime cancer risk CDI x Potency
  factor
• CDI (mg/kg-day) Average daily dose (mg/day) /
  Body weight (kg)

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Toxicity Data for Selected Potential Carcinogens
(USEPA, IRIS (1989))
Chemical Potency factor inhalation route (mg/kg-day)-1
Arsenic 50
Benzene 0.029
Benzol(a)pyrene 6.110
Cadmium 6.100
Chloroform 0.081
Chromium VI 41.000
1,1-Dichloroethylene 1.160
Methylene chloride 0.014
Nickel and compounds 1.190
Tetrachloroethylene 0.003
Trichloroethylene (TCE) 0.013
Vinyl chloride 0.295
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Predicted Carcinogens Ground Level Concentrations
Compound Average concentration (µg/m3) Average concentration (µg/m3) Average concentration (µg/m3) Average concentration (µg/m3)
Compound within 100 m At 500 m At 1 km At 2 km
1,1-Dichloroethene 0.194 0.159 0.006 0.003
Benzene 1.493 1.218 0.0479 0.024
Chloroform 0.036 0.029 0.001 0.0006
Tetrachloroethylene 6.187 5.047 0.198 0.101
Trichloroethylene 3.705 3.022 0.119 0.061
Vinyl chloride 3.57 2.912 0.114 0.058
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Isopleths of average vinyl chloride concentration
(ng/m3)
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Estimated Lifetime Cancer Risk
Compound Incremental Lifetime Cancer Risk Incremental Lifetime Cancer Risk Incremental Lifetime Cancer Risk Incremental Lifetime Cancer Risk
Compound within 100m At 500m At 1km At 2km
1,1-Dichloroethene 2.6E-05 2.17E-05 8.17E-07 4.086E-07
Benzene 5.1E-06 4.15E-06 1.63E-07 8.172E-08
Chloroform 3.4E-07 2.76E-07 9.51E-09 5.706E-09
Tetrachloroethylene 2.4E-06 1.96E-06 7.67E-08 3.913E-08
Trichloroethylene 5.7E-06 4.61E-06 1.82E-07 9.311E-08
Vinyl chloride 1.246E-04 1.01E-04 3.81E-06 1.73E-06
Total Risk 0.00016 0.000134 5.2E-06 2.637E-06
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Isopleths of cancer risks (10-3) due to vinyl
chloride
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Survey of Landfill Site
Sl. No. Age Service (in years) Exposure Residence Number of cancer symptoms Any disorder
1 50 8 10 hrs/per day gt1km 0 yes
2 38 10 7 hrs/per day gt1km 2 yes
3 31 10 10 hrs/per day gt1km 2 yes
4 35 12 8 hrs/per day gt1km 5 yes
5 40 14 8 hrs/per day gt1km 0 yes
6 60 25 7 hrs/per day gt1km 4 yes
7 55 25 9 hrs/per day gt1km 2 yes
8 58 30 10 hrs/per day gt1km 0 yes
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A Construction Site
Sl. No. Age Service (in years) Exposure Residence Number of cancer symptoms Any disorder
1 30 8 8 hours/per day lt1km 0 yes
2 28 10 8 hours/per day gt1km 0 no
3 41 11 8 hours/per day lt1km 0 no
4 45 25 8 hours/per day gt1km 2 yes
5 32 13 8 hours/per day lt1km 0 no
6 25 5 8 hours/per day lt1km 0 no
7 25 2 8 hours/per day lt1km 0 no
8 48 20 8 hours/per day lt1km 3 yes