Solid Waste Gases: Odor Threshold, Toxicity

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Solid Waste Gases Odor Threshold, Toxicity Risk

• Prof. Gary Winston
• Chief Toxicologist
• Israel Ministry of Health

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Paracelsus (1493 1541) The Father of Toxicology
An old woodcut describes Paracelsus' theories
of alchemistic medicine.
The dose makes the poison
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Municipal sludge, solid waste, landfills and
composting all generate odors that can be
offensive to a community. Different types of
solid waste generate diverse odors. Municipal
wastewater sludge generally make sulfides while
composting generally emits nitrogen compound
odors. Mercaptans from municipal solid waste
landfills are a major nuisance.
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Typical Constituents of Municipal Solid Waste
Landfill Gas Component                           
            Percent (dry volume) Methane         
                                 
        40-60Carbon Dioxide                     
                   40-60Nitrogen                
                                     
 2-5Oxygen                                      
             0.1-1.0Ammonia                     
                           0.1-1.0 Sulfides,
disulfides, mercaptans             0-0.2Hydrogen
                                                 
 0-0.2Carbon Monoxide                           
           0-0.2Trace Constituents              
                   0.01-0.6 Exact percentage
distribution varies with age of landfill.
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• Three ways in which odors are associated with
  health symptoms.
• 1. Exposure to odorant (e.g. ammonia vapor) at
  levels that can produce symptoms of sensory
  irritation. Irritancy occurs at a level above
  but within an order of magnitude of the odor
  threshold.
• At concentrations gt irritation threshold, the
  experience of odor occurs simultaneously with
  irritation, but symptoms are caused by irritation
  rather than odor-induced.
• In this case odor is simply a warning of
  potential health effects at elevated
  concentrations.

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• 2. The odorant is part of a mixture but a
  co-pollutant with no odor is responsible for the
  health symptom. For example, simultaneous
  exposure to odors from sludge and bacteria.
• To the extent that symptoms are a result of
  bacterial exposure, odor is merely acting as a
  marker of exposure.

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• 3. Exposure to odorants that are 3-4 orders of
  magnitude below levels that cause irritation or
  classical toxicological symptoms. Examples are
  sulfur-compounds such as H2 S, mercaptans and
  thiophenes.
• Concentrations above odor threshold but below
  irritant levels is associated with increased
  symptom reporting.
• Need to understand the complex interplay between
  biological, behavioral and psychosocial factors
  on expression of health symptoms from odors.

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• Chemical Formula O.T. (ppm) T.T. (ppm)
• Hydrogen Sulfide H2S 0.001 - 0.13 TLV
  10
• MAC 10
• ILDH 100
• Methyl Mercaptan CH3SH 2x10-7 0.04 TLV
  0.5
• MAC 0.5
• ILDH 150
• Carbon Disulfide CS2 0.01 0.42 TLV 10
• MAC 5
• ILDH 500

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Risk Assessment
Dose-Response Assessment Noncarcinogens

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Characterizing Risk for Non-carcinogens

RfC NOAEL or LOAEL UF NOAEL OR LOAEL
for critical effect
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Characterizing Risk for Non-carcinogens

• Permissible Concentrations for chemicals in the
  environment
• RfC x Body Weight
• Intake x Duration x Frequency
• Values used to set regulatory standards such as
  MCLs for drinking water, MRLs for pesticides in
  food and PELs in the work place.

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Risk Assessment
Dose-Response Assessment Cancer Effects

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Characterizing Risk for Carcinogens

• LADD Cair x IR x EF x ED
• BW x AT
• Cair Concentration in air (mg/m3)
• IR Inhalation Rate (m3/day)
• EF Exposure Frequency (days/yr)
• ED Exposure Duration (years)
• BW Body Weight (Kg)
• AT Averaging Time (days)

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Characterizing Risk for Carcinogens

• Potential Cancer Risk
• LADD x Cancer Slope Factor
• For Benzene
• LADD 0.134 mg/kg/day
• Cancer Slope Factor 2.7 x 10-2 per mg/kg/day
• So PCR 3.6 x 10-6