Composting Odors by dfgh4bnmu


									     Perception and physiological effects
       of agents possibly emitted from
      commercial composting facilities

  Statewide Organics Management Meeting, Ellensburg WA
                     September 9, 2009
Matt Kadlec, PhD, DABT, Air Quality Program Senior Toxicologist
   Composting emissions that make odors
                                 Primary Odor Constituents
                                 • Organic sulfur-containing
                                   compounds, especially
                                   dimethyl sulfide, identified
                                   as the primary odorants
Composting is a complex             – sometimes hydrogen sulfide
biological process, and the
potential for the formation of
                                 • Organic acids, such as
odorous compounds is
                                    – acetic, propionic, butyric,
virtually limitless                   valeric, and caproic acids ,

Feedstock affects emissions      • Ammonia and amines
(gypsum, feathers, meat)           produced with high-
                                   nitrogen-containing wastes
                                   (C:N below 15:1)
Compound Name                Odor Descriptors             Compound Name           Odor Descriptors
                   Volatile Fatty Acids                                  Nitrogen Compounds

Formic acid                  Biting, Pungent              Ammonia                 Pungent, Sharp

Caproic acid                 Pungent                      Ethylamine              Ammonia-like
                             Rancid butter, Body odor,    Indole                  Fecal
Butyric acid
Iso-valeric acid             Rancid cheese                Skatole                 Fecal

Propionic acid               Rancid, Pungent              Trimethylamine          Fishy, Pungent

Capric acid                  Rancid, Soil                 Dimethylamine           Rotten fish

Valeric acid                 Sweat                        Cadaverine              Putrid, Decaying flesh

Acetic acid                  Vinegar, pungent             Methylamine             Putrid, Fshy

                   Sulfide Compounds                      Putrescine              Putrid

Carbon disulfide             Sweet, Rotten pumpkin                      Ketones and Aldehydes
                             Pungent, Rotten cabbage,     Formaldehyde            Acrid, Medicinal
                             Skunk, Garlic
                                                          Acetaldehyde            Sweet, Fruity
Dimethyl disulfide           Putrid, Sulfurous
                                                          Phenol                  Medicinal
Ethyl-mercaptan              Rotten cabbage, Leek-like
                                                          Acetone                 Pungent, solvent
Hydrogen sulfide             Rotten egg
                                                          Methyl ethyl ketone     Sweet, Solvent
Dimethyl sulfide             Sulfurous, Rotten cabbage,
                      Olfactory epithelium
    Odor molecules dissolve in a mucous
    layer covering the olfactory
    neuroepithelium, which overlays
    cartilage in the back of the nasal cavity
•   Each of the ~50 million olfactory neurons
    in this epithelium extends a ciliated
    dendrite to the surface epithelial layer
    and overlaying mucus
•   Receptors on different cells have
    different specificities. There are 350 or
    more odorant receptor genes
•   The system can distinguish up to 10,000
      – (1) single receptors can recognize
         multiple odorants
      – (2) a single odorant is typically
         recognized by multiple receptor
      – (3) different odorants are recognized
         by different receptor combinations
            Vulnerable olfactory tract
• Unlike other neurons, OSNs
  regenerate to maintain
  olfactory function (30 to 40-day
• But unlike the rest of the brain,
  there is no protective blood-
  brain barrier
• Because the OE is in direct
  contact with the environment,
  airborne chemical toxicants
  and infectious microbial
  agents, may induce cell injury
  and death of OSNs
• Inhaled materials, including
  fine airborne particles, may
  enter the central nervous
  system via olfactory nerves
                                  Cranial nerves
•   Two separate nerve systems are at work,
    each creating a different type of sensation
    in response to airborne chemicals

•   The first cranial nerve, or olfactory nerve,
    generates perceptions associated with the
    qualities of odor

•   The fifth cranial, or trigeminal nerve,
    produces sensations of irritation or

•   Odor sensations from the olfactory nerve
    apparently do not produce a physiological
    response. However, sensations from the
    trigeminal can produce responses such as a
    running nose, red eyes or sneezing, when
    an irritant, like ammonia, is detected in
    sufficient quantity

•   The brain combines these into a single
    perception of the odor
    Olfactory brain function

•   Peripheral olfactory neurons project to the olfactory bulb from
    which signals are relayed to the olfactory cortex and more
    primitive structures including the hippocampus and amygdala

•   The limbic system - emotions, behavior, and memory storage

•   Signals go to the cortex, or outer layer, where conscious
    thought occurs, as well as to the vomit center
    Odor dimensions

• There are four odor dimensions:

  – Detectability
  – Intensity
  – Character
  – Hedonic tone
• The lowest concentration of an odor that can be
  detected / recognized
   – odor detection/recognition thresholds: usually the population mean

• The difference in concentration between detection and
  recognition thresholds typically varies from twofold to

• Detection thresholds are more commonly reported
  than recognition thresholds

• Detecting a smell without recognizing the chemical(s)
  may not give sufficient warning
           Population distribution of
             olfactory sensitivity
• Olfactory acuity in the
  population conforms to
  a normal distribution
• Most people, assumed
  to be about 96% of the
  population, have a
  “normal” sense of smell
• 2% are assumed to be
  hypersensitive and 2%
• Adaptation to an odor, also known as olfactory fatigue

• A temporary desensitization after smelling an odor.
  Individual receptors desensitize with use, temporarily
  losing their ability to transduce signals

• After smelling a strong odor, a weaker near-threshold
  odor may not be detectable

• Occurs rapidly. After three minutes of exposure to an
  odorant, perceived intensity is reduced about 75%
• The perceived strength of the odor sensation
• Increases as a function of concentration
• Categories:
   –   0 - no odor
   –   1 - very weak (odor threshold)
   –   2 - weak
   –   3 - distinct
   –   4 - strong
   –   5 - very strong
   –   6 - intolerable
• Ability to discriminate between different odor intensities is
  very sensitive
• Generally concentrations higher or lower by 25 to 33% are
  perceived as different
• In one study, the average perceptible difference was 11 %,
  ranging from 5 to 16% for different compounds
Relative intensity/concentration slopes
   of ammonia and hydrogen sulfide
                                      • At high concentrations of both, the
                                        predominant odor will be NH3,
                                        while at lower concentrations, H2S
                                        will be detected (masking)

                                      • Slope also describes the degree of
                                        dilution necessary to decrease the
                                          – A lower slope value indicates an odor
                                            that requires greater relative dilution
                                            for the odor to dissipate
                                          – A higher slope value indicates an odor
                                            that can more quickly be reduced by
                                          – H2S carries farther offsite than NH3

• The steep slope for ammonia as      • H2S and amines have low slopes
  compared to the shallow slope for   • NH3 and aldehydes have high slopes
  hydrogen sulfide
        Ranked composting chemical
             odor intensities
1.   Sulfur compounds           The emitted
2.   Fatty acids                mass of
3.   Amines and Ammonia         ammonia is
                                often more than
4.   Terpines                   the masses of
5.   Phenol, Acetone, Toluene   other compound
• What the substance smells like
• A description of the odor, e.g., sweet, pungent
• Odor character may change with concentration. Large
  amounts of a chemical bind to a wider variety of
  receptors than do small amounts of the same chemical
   – e.g., small amounts of skatole are used in some perfumes
     because low levels smell good, but high levels smell like
     excrement; a trace of indole smells flowery but a large
     whiff smells putrid
• People equate bad odors with bad things. Odors imply
  risks, hazards and danger to many people
         Hedonic tone
• A judgment of the relative pleasantness or
  unpleasantness of an odor

• An odor may be unpleasant to one person and
  agreeable to another person. Some odors are
  generally considered unpleasant: ammonia ,
  hydrogen sulfide, cadaverine

• Individual reactions are related to gender, age,
  state of health, and personal judgment

• Influenced by such factors as subjective
  experience, frequency of occurrence, odor
  character, odor intensity, and duration (You might
  start hating a smell after being in it to too long)
             Sensory irritation
• Becomes more severe as the exposure time
• Adverse sensory reactions to strong odors and
  irritants, such as ammonia, may lead to the
  release of catecholamines and stress hormones
• Higher catecholamine levels can increase
  cardiovascular health risks: blood pressure, heart
  rate, high-density lipoprotein (HDL) cholesterol
  level and serum triglyceride level
             There a Link Between Odor
                    and Toxicity?
• Chemical mixtures can present odors that may or may not reflect the
  hazard potential of the chemical constituents

• Mechanisms involved with odor detection have little to do with the
  mechanisms involved chemical-induced toxicity and carcinogenesis

• Odorants need not be strong toxicants and toxicants need not be

• Detecting and identifying a chemical by odor in combination with
  information and toxic potency can be useful in cases where the odor
  threshold concentration is known and can be compared to a health-
  based concentration
 Exposure        Duration   Effects

20                          Decreased disease resistance
50                          Smell
50               < 1 day    Eye and throat irritation, Severe cough
100              6 weeks    Impaired pulmonary function
<150             < 1 day    Scarring of upper and lower airway
500              30 min     Sore nose and throat
<1000                       Irritation of upper respiratory tract
>4000                       Severe damage to upper and lower respiratory tract
5000             < 30 min   Death
•   The WHO recommended 30-minute
                                     Hydrogen sulfide
    average H2S concentration not exceed 5                                      Proportion of the general population who
    ppb (7-µg/m3) in order to avoid
    substantial complaints about odor
                                                                                experience “annoying” effects with brief
    annoyance                                                                   exposures at different concentrations

•   11-µg/m3 odor threshold

•   1-5-ppm nausea eye irritation headache,

                                                       Cumulative Resp.
    insomnia (with prolonged exposure)                                    0.6

•   30-ppm induces lesions in olfactory
    mucosa. odor becomes sickeningly sweet

•   100-ppm leads to olfactory paralysis                                  0.2

    which prevents detection of odor
     –   More occupational deaths than any other gas
                                                                                       50       100      150       200      250        300
•   Younger people are more sensitive to the                                                             g/m3
                                                                                “Annoying” effects defined as physiological effects,
                                                                                including nausea and headache, and esthetic and
•   Long-term, low-level exposure can result
                                                                                behavioral responses at slightly higher
    in fatigue, loss of appetite, and headaches
                                                                                concentrations (Amoore and Hautala, 1983)
  (µg/m3)                                            Conc.
                Odor       Odor                                  Risk
                                        Odor       factor to
              detection recognition                          concentrati               Effects
                                     character      double
             Geo Mean geo mean                                    on
                                                              3200 (1-h Irritant
 Ammonia     262, 3540     3330     Urine, pungent              REL):
                                                              100 (RfC)
                                                                         Respiratory irritation; Lesions of
                                                                         the olfactory mucosa;
 Hydrogen                                                     42 (1-h);
                  11        110      Rotten eggs      4.8                cytochrome oxidase inhibitor;
   sulfide                                                    2 (24-hr)
                                                                         headache; exacerbation of
                                                                         seizure disorders
                                                              9 (24-hr); Sensory irritation - eye redness
Acetaldehyde     120                   Pungent                 0.37 (yr) and swelling; Degeneration of
                                                               EPA and olfactory epithelium; Carcinogen
  Methyl                                  Decayed                  1 (8-h TWA Irritant; CNS depressant
                   1            2         cabbage
 mercaptan                                                            PEL)
                                                                              Smell becomes highly
  Dimethyl                                Decayed                             disagreeable at higher
               2.6, 155       14.5                                     0.26
   sulfide                                cabbage                             concentrations.
                                                                              Resp. irritation > 388,000
  Dimethyl                               Sulfurous,                           Irritating to eyes
                  188                  cabbage, onion
                                                         8 - 10    1960 (TLV)
   Indole         0.81                  Fecal, Putrid      8
                                        Rancid butter,
  Butyrate        0.7                     garbage
                                                         10 - 20

  Skatole         6.55        2560          Fecal
                    Community effects
Symptoms in response to
composting NH3, H2S,VOCs, etc.

• Nausea
• Headache
• Runny nose
• Coughing
• Burning eyes, nose, throat
• People with allergic inflammation are likely to be more
  sensitive to VOC-caused eye, nose and throat irritation
• Negative mood (anger, tension, depression, fatigue,
• Shortness of breath
• Drowsiness
Are the symptoms real (physiological) or perceived (psychological)?
 Are composting emissions just a nuisance
 or are they a significant risk to people or
            the environment?
• Unpleasant odors –> stress, aesthetic effects
  diminished quality of life and property values,
  induction of multiple chemical sensitivity?
• Ammonia        –> deposition, odor, irritation
• H 2S           –> odor, health
• PM and NOx –>haze, health
• N20 and CH4 –> climate
• NOx + VOC      –> ozone
• Bioaerosols    –> infection, ODS, allergy, toxins…
                 Bibliography of Research
                          Further Reading
ASTM E544 - 99(2004) Standard Practices for Referencing Suprathreshold Odor Intensity.
Active Standard ASTM E544 Developed by Subcommittee: E18.04 Book of Standards
Volume: 15.08

Krzymien et al., 1999, Journal of the Air & Waste Management Association 49(7):804-

Leffingwell. 2002. Olfaction – Update No. 5. Leffingwell Reports, Vol. 2 (No. 1),
Leffingwell & Associates

Morand et al., 2005.; Gaseous Emissions from Composting Bark/Manure Mixtures
Compost Science & Utilization; Winter pg. 14

Ninth Meeting of the Scientific Advisory Board (SAB) on Toxic Air Pollutants. Proceedings
of the April 17, 2001 Meeting. on 10-15-07

Smith et al., 1999. Cardiovascular effects of odors. Toxicol. Ind .Health 15(7):595-601

San Diego State University. Contractor’s Report to the Board: Comprehensive Compost
Odor Response Project. March 2007. Integrated Waste Management Board Publication #

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