44 BIOCYCLE NOVEMBER 2007

OVER THE years, there havebeen concerns related to work-er and neighbor health due toairborne particles emittedfrom composting operations.As a result, there has been asteady stream of studies to

evaluate these impacts. This report sum-marizes a comprehensive review of the lit-erature, providing citations to relevantjournal articles and published governmen-tal reports. It has been compiled to help ad-dress questions regarding the potential ofair emissions from large-scale compostingfacilities to impact the health of neighbors.

There has been a significant contributionto the literature in the past decade, in partdue to studies supported by the EuropeanCommission. Much of the available litera-ture addresses on-site investigations rele-vant to worker health. Some of the litera-ture on worker health is summarizedbecause of its relevance to neighbor im-pacts. However, no attempt has been madeto comprehensively address worker healthrelated to air emissions at compost facili-ties. In addition, this summary does not in-clude a comprehensive review of odor orvolatile organic compound studies.

This article is an abridged version of a lit-erature summary that includes papers thataddress air emissions and monitoring ofbioaerosols as well as health. The unabridgedreport can be found at http://cwmi.css.cor-nell.edu/compostairemissions.pdf.

GENERAL OBSERVATIONSFROM THE LITERATURE

Bioaerosols: Airborne particles of concernrelated to composting fall into the generalcategory of bioaerosols. Bioaerosols are par-ticles of microbial, plant or animal origin andmay be called organic dust. They can includelive or dead bacteria, fungi, viruses, aller-gens, bacterial endotoxins (components ofcell membranes of Gram-negative bacteria),antigens (molecules that can induce an im-mune response), toxins (toxins produced bymicroorganisms), mycotoxins (toxins pro-duced by fungi), glucans (components of cellwalls of many molds), pollen, plant fibers, etc.Many bioaerosols are released or produced bythe composting process. Microorganisms arefrequently absorbed onto dust particles andwill be transported along with the dust.Available data are not sufficient to determinewhether there is a relationship between dif-ferent compost feedstocks and the type andconcentration of bioaerosols emitted.

Many bioaerosols are known to causesymptoms and/or illness, including a widerange of adverse health effects and infec-tion. Individuals may become increasinglysensitized to some bioaerosols through re-peated exposure. There are no ambient oroccupational exposure limits for bioaerosolsin the U.S.

Variation in exposure to bioaerosols fromcomposting facilities is high even overshort time periods. Intermittent releases

and changes in wind complicate air moni-toring since sampling other than for shorttime intervals can be difficult. A number ofstudies show that concentrations ofbioaerosols downwind of outdoor compost-ing facilities are elevated above back-ground at times to distances on the order of200 to 500 meters (650 to 1640 feet). Con-centrations of bioaerosols in enclosed com-posting facilities are significantly elevated.

Monitoring Methods : Monitoringbioaerosols is a challenge. Monitoring in-volves collecting air samples using one ormore types of collection devices and thenanalyzing samples for selected microorgan-isms and nonliving bioaerosols. All moni-toring methods underestimate bioaerosolconcentrations due to the spatial and tem-poral variability of airborne concentrations,the difficulty of keeping the microorgan-isms alive through the collection processand the limitations of the detection andenumeration processes. Validated standardmethods are not yet available for measur-ing the various bioaerosols. Use of culturetechniques in which samples are treated togrow selected organisms will underesti-mate potential health risks since viable,nonculturable microorganisms — as well asnonliving constituents — can contribute tohealth risks.

Direct spore counts can provide a some-what better estimate of exposure for irri-tation and allergic reactions, but cannotdetermine viability and thus potentialfor infection. This method still underesti-mates exposure to particulates and piecesof bacteria (endotoxin), spores and fungalhyphae, which also can produce irritation,allergy and toxic reactions. Direct sporecounts cannot distinguish between somespecies (such as penicillium andaspergillus), making exposure indetermi-nant. DNA analysis methods using PCRtechnology are being developed for moreand more species, but are still limited inwhat types of organisms can be identified.

There have beensignificantcontributionsto the literatureon compostingoperations inthe past decade.Most addresson-siteinvestigationsrelevant toworker health.

Ellen Z. Harrison

LITERATURE REVEIW

HEALTH IMPACTSOF COMPOSTINGAIR EMISSIONS

CompostResearch

BIOCYCLE NOVEMBER 2007 45

Aspergillis fumigatus is ubiquitous inboth outdoor and indoor (particularlywhere there are pets) air. It is a bioaerosolthat is often measured because it is knownto be emitted during composting. Howev-er, measuring A. fumigatus is not a goodindicator for other bioaerosols since therelative abundance of A. fumigatus com-pared to other microbes varies seasonallyin air emissions from composting facilities.

Health Effects: Health effects that havebeen noted include respiratory symptoms,muscosal membrane irritation, skin dis-eases and markers showing immune sys-tem response. An association was found inresidents between distance to an outdoorcomposting facility and respiratory symp-toms and general health complaints, butnot allergies or infectious disease. Self-re-ported symptoms were not correlatedwith A. fumigatus levels in the air in thevicinity of a large open-air yard wastecomposting facility.

Compost workers show a response toelevated exposure to bioaerosols despitethe fact that there is a “healthy worker”effect. For numerous reasons, workerstend to be healthier than the populationin general and particularly the part ofthe population at relatively high risk. Asample drawn only from workers has aselection bias since obviously some of themost sensitive populations (children, theelderly, people with illnesses) are not in-cluded and additionally, workers thatexperience adverse health effects whichthey find intolerable will seek employ-ment elsewhere, leaving the “survivors”or “hardy” workers.

Acute and chronic respiratory healtheffects, mucosal membrane irritation,skin diseases and inflammatory markerswere elevated in workers. Short-term ex-posure to air in an enclosed compostingfacility resulted in measurable systemicchanges in healthy subjects that werenot compost workers. Occupational ex-posure to bioaerosols may be reducedthrough a combination of engineeringcontrols, work practices (and other ad-ministrative controls), and personal pro-tective equipment.

Compost Process Management: Agita-tion of the compost (such as turning andscreening) produces emissions. Minimiz-ing agitation, application of water tominimize dust, and monitoring wind toavoid agitation when winds are likely toblow towards neighbors can help mini-mize impacts.

Good management of composting canhelp minimize odor impacts, however,odors are generated even at well-managedcompost facilities. Odors are caused bychemical emissions and are notbioaerosols (this article does not provide areview of the odor literature). Compoundscausing odors are not generally presentoff-site at concentrations high enough tocause illness, however excessive odors can

result in symptoms such as nausea. Odors are minimized when there is ad-

equate oxygen, and oxygen is best con-trolled through ensuring free air spaceby using amendments like wood chipsthat improve porosity. A blanket of fin-ished compost on top of unfinished pilescan reduce odor and VOC (volatile or-ganic compound) emissions. There areno data to demonstrate whether it willreduce bioaerosol emissions.

LITERATURE SUMMARIESIn this article, as well as the

unabridged report, the summaries arearranged in chronologic order of publica-tion date, starting with the most recent.The choice to place the summaries inchronologic order is based on the factthat much of the relevant literature isvery recent and thus earlier articles(generally those prior to 2000) that drawconclusions based on the literature thatwas then available are out of date.

Bunger, J., B. Schappler-Scheele, R.Hilgers, and E. Hallier. 2006. A 5-YearFollow-Up Study on Respiratory Disor-ders and Lung Function in Workers Ex-posed to Organic Dust from CompostingPlants. International Archives of Occu-pational and Environmental Health. On-line: http://www. springerlink.com/con-tent/82u23r2371414873/fulltext.pdf

Conclusion: Exposure to organic dustat composting workplaces is associatedwith adverse acute and chronic respira-tory health effects. Compost workerswere compared to controls at 41 Germancompost facilities (mixed householdbiowaste plus yard wastes). Exposuremeasurements revealed high concentra-tions of fungi and actinomycetes. Com-post workers report significantly higherprevalence of mucosal membrane irrita-tion of eyes and upper airways as well asmore conjunctivitis. A significant declinein forced vital capacity was measured.Results differ from workers exposed toorganic dust in other facilities, andmaybe due to thermotolerant fungi andbacteria in compost plants.

Muller, T., R. A. Jorres, E. M. Scharrer,H. Hessel, D. Nowak, and K. Radon. 2006.Acute Blood Neutrophilia Induced byShort-Term Compost Dust Exposure inPreviously Unexposed Healthy Individu-als. International Archives of Occupation-al and Environmental Health. 79:477-482.

Conclusion: Short-term exposure ofhealthy young subjects to organic dust atcomposting facilities had mild but mea-surable effect in eliciting acute systemicalterations. 17 healthy subjects not work-ing with wastes were exposed at a com-posting facility for two hours doing mod-erate exercise. Changes in white bloodcell counts, an increase in neutrophils anddecrease in eosinophils were measured.

46 BIOCYCLE NOVEMBER 2007

Wouters, I. M., S. Spaan, J. Douwes, G. Doekes, and D.Heederik. 2006. Overview of Personal Occupational ExposureLevels to Inhalable Dust, Endotoxin, �(1 >3)-Glucan andFungal Extracellular Polysaccharides in the Waste Manage-ment Chain. Annuals of Occupational Hygiene. 50(1):39-53.

Conclusion: Worker “exposure variability is large, with greaterwithin-worker than between-worker variance. Occupational ex-posure limits for organic dust and endotoxins are frequently ex-ceeded, suggesting workers are at risk of developing adversehealth effects.” Worker exposure was monitored in one indoorfacility composting household waste, as well as a second studythat involved 13 facilities (3 residential organic wastes — in-doors; 6 green waste — outdoors; 4 mixed residential organicwastes and green waste — indoors). Endotoxin and dust levelsat residential organic waste and mixed composting facilitieswere higher than at green waste sites; endotoxins at such facil-ities often exceed Dutch occupational standards. Highest expo-sure occurs where waste is disturbed. Within-worker variationin exposure, associated with different tasks and locations, wasgenerally higher than between-workers. Variation in bioaerosolcomposition of dust was high. Caution is required in comparingdifferent studies due to method differences.

Herr, C. E. W., A. zur Nieden, H. Seitz, S. Harpel, D. Stin-ner, N. I. Stilianakis, and T. F. Eikmann. 2004. Bioaerosolsin Outdoor air — Statement of Environmental Medical As-sessment Criteria on the Basis of an Epidemiological CrossSectional Study. Gefahrstoffe Reinhaltung Der Luft.64(4):143-152.

Conclusion: There was an association between irritativerespiratory symptoms and general health complaints anddistance to the site. There was no higher prevalence of re-ported allergies or infectious diseases. Total bioaerosols (to-tal bacteria, molds and thermophilic actinomycetes) werefound at >105 CFU/m3 in outdoor air in the vicinity of an out-door composting facility, dropping to background concentra-tions within 550 m. Individual odor annoyance was not as-sociated with symptoms.

Herr, C. E. W., A. zur Nieden, N. I. Stilianakis, and T. F.Eikmann. 2004. Health Effects Associated With Exposure toResidential Organic Dust. American Journal of IndustrialMedicine. 46:381-385.

Conclusion: An association was demonstrated between resi-dential bioaerosol pollution and irritative airway complaints aswell as excessive fatigue and shivering (symptoms that are re-ported at workplaces handling such materials). Significantlyhigher than background concentrations of thermophilic actino-mycetes, total bacteria and molds were measured in air down-wind within 200 m from an outdoor composting site (type offeedstock not specified), dropping to near background within300 m. The highest levels measured within 200 m of the site(>105CFU/m3) are similar to occupational composting expo-sures. A physician-administered survey found airway symp-toms; no odor annoyance was observed in residents in highestexposure (150-200 m downwind) vs. further away (400-500 m).Residents reporting odors did not “overreport” health distur-bances, indicating that odors did not bias reports of illness.

Douwes, J., P. Thorne, N. Pearce, and D. Heederik. 2003.Bioaerosol Health Effects and Exposure Assessment:Progress and Prospects. Annals of Occupational Hygiene.47(3):187-200.

Conclusion: Risk assessment for bioaerosols is “seriously ham-pered by the lack of valid quantitative exposure assessment meth-ods.” This is a review article. Culture methods for measurementof bioaerosols is more qualitative than quantitative. It has poorreproducibility, does not measure some organisms and does notmeasure nonliving constituents. Nonculture methods rely on mi-

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croscopes or flow cytometry to identify andcount. “Traditional culture methods to quan-tify microbial exposures have proven to be oflimited use … many biological agents thatmay cause health effects are currently notidentified. For instance, sewage treatmentworkers have an increased risk of developinga wide range of symptoms including respira-tory, gastrointestinal and neurological symp-toms, whereas causal agents have not beenidentified.”

In general, exposure to bioaerosols can beassociated with a wide range of adversehealth effects (including contagious dis-eases, acute toxic effects, allergies and can-cer as well as possibly preterm births or lateabortions and dermatitis). Workers in thewaste industry are often exposed to veryhigh levels of microorganisms and severalstudies indicate high prevalence of respira-tory symptoms and airway inflammation.Diseases and symptoms associated with var-ious bioaerosol components are described.

Herr, C. E. W., A. Zur Nieden, R. H.Bodeker, U. Gieler, and T. F. Eikmann.2003. Ranking and Frequency of SomaticSymptoms in Residents Near CompostingSites With Odor Annoyance. InternationalJournal of Hygiene and EnvironmentalHealth. 206:61-64.

Conclusion: Residents living near one ofthe sites at which concentrations of microor-ganisms were high experienced increasedsymptoms relative to the control population.

Nausea was associated with strong odors.This brief paper reports results of an epi-demiologic study of people living in the vicin-ity of three composting plants.

Browne, M. L., C. L. Ju, G. M. Recer, L.R. Kallenbach, J. M. Melius, and E. G.Horn. 2001. A Prospective Study of HealthSymptoms and Aspergillus fumigatusSpore Counts Near a Grass and Leaf Com-posting Facility. Compost Science and Uti-lization. 9(3):241-249.

Conclusion: Participant diaries showed nocorrelation between symptoms and A. fumi-gatus concentrations. Aspergillis fumigatusspore concentrations are higher in vicinity ofa 40-acre yard waste composting site thanbackground. The study used self-reportingthrough diaries to record symptoms, howev-er there are caveats: large short term varia-tions in concentrations of A. fumigatus weremeasured and the spore counts used were av-erages and were taken at sampling locationsnot specific to personal exposures. No otherbioaerosols were measured.

Wheeler, P. A., I. Stewart, P. Dumitrean,and B. Donavan. 2001. Health Effects ofComposting — A Study of Three CompostSites and Review of Past Data. TechnicalReport P1-315/TR. Pages 111. UK Environ-ment Agency.

Conclusion: “Composting activities do emitbioaerosols at levels which can pose a hazardto susceptible members of the public.” This isa literature review and report on monitoringof emissions from three composting plants(two green waste turned windrow facilitiesand one mixed waste in-vessel facility). Abuffer zone of 250 m around composting sitesis suggested. Concentrations for total bacte-ria of 1000 CFU/m3, 1000 CFU/m3 for totalfungi, 300 CFU/m3 for gram-negative bacte-ria and 250 �g/m3 for inhalable dust are sug-gested as conservative (low) protective val-ues. These concentrations are generallyexceeded at composting sites (105-106

CFU/m3 of bacteria and gram negative bac-teria and 103-104 CFU/m3 of fungi were mea-sured), suggesting the value of respiratoryprotection for workers. Under most condi-tions, concentrations decline to these levelswithin a distance of 250 m from compost fa-cilities. Emissions measured onsite fell with-in the range of 103-107 fungi and bacteriaduring compost agitation. Due to clumping ofbacteria and overloading of Andersen sam-plers, bacterial concentrations measured us-ing a filter method were approximately 10times higher than those measured with anAndersen sampler. While generally concen-trations declined with increasing distance, insome cases concentrations peaked a shortdistance from the operation. The significantlevels of biological agents in clothing of com-post workers suggests that families may beexposed if workers take clothes home.

Bunger, J., M. Antlauf-Lammers, T.Schulz, G. Westphal, M. Muller, P. Ruh-

48 BIOCYCLE NOVEMBER 2007

WHEN evaluating steps thatminimize potential health im-pacts from a composting fa-

cility, the most important is to con-sider appropriate managementpractices and facility design that suitthe site and the materials. For exam-ple, compost facilities at sites inclose proximity to people may needto be enclosed in order to control airemissions. The possibility of reduc-ing potential health impacts by fol-lowing good practices is recognized(Millner, et al., 1994).

Recommendations to minimizeimpacts include:

Siting• Consider how meteorological

and topographic features affect airflow

• Establish buffers between re-ceptors and the composting facility

Design• Site material handling processes

downwind or maximum distancefrom receptors

• Enclose facilities to reduce off-site exposures if needed

• Install pad type suited to the op-eration

• Minimize ponding through sitegrading and design

Operation/Management• Maintain good air flow through

the compost• Minimize handling• Turn compost based on temper-

atures, not a schedule • Restrict material movement to

times when the potential for off-sitemovement is minimal (low wind) andreceptor population is least (time ofday, avoid weekends and holidays)

• Minimize disturbance of dustyareas by equipment

• Minimize dust by adding mois-ture to materials when moving themand to traffic areas, and watering drymaterials and dusty areas

RECOMMENDATIONS TO MINIMIZEPOTENTIAL HEALTH IMPACTS

50 BIOCYCLE NOVEMBER 2007

nau, and E. Hallier. 2000. Health Com-plaints and Immunological Markers ofExposure to Bioaerosols AmongBiowaste Collectors and CompostWorkers. Occupational and Environ-mental Medicine. 57:458-464.

Conclusion: Compost workers had sig-nificantly more symptoms and diseasesof the airways and skin than control sub-jects. Some workers quit due to airwaycomplaints leading possibly to underes-timation of health effects. Increased an-tibody concentrations against fungi andactinomycetes were found in compostworkers. There was an association be-tween the diseases and increased anti-body concentrations in compost workers.A “healthy worker” effect is indicated bythe under representation of atopic (aller-gic) diseases among compost workers.

Douwes, J., I. Wouters, H. Dubbeld, L.v. Zwieten, P. Steerenberg, G. Doekes,and D. Heederik. 2000. Upper Airway In-flammation Assessed by Nasal Lavage inCompost Workers: A Relation With Bio-Aerosol Exposure. American Journal ofIndustrial Medicine. 37(5):459-468.

Conclusion: “Compost workers are atrisk of developing acute and possiblychronic inflammatory responses in theupper airways…” Workers in a compostplant that stored and processed source-separated food and yard waste indoorswere studied using nasal lavage (NAL)(in which fluid is inserted in the nose andthen removed and analyzed for variousmarkers). The study included two timeperiods, one before and one after processimprovements were made to try and de-crease exposure to bioaerosols in the fa-cility. Bioaerosols were lower after pro-cess improvements, however nasal andrespiratory symptoms were unchanged.Compared with controls, before the facil-ity improvements the workers had high-er indicators inflammatory markerseven on Monday morning before work.Comparing pre- and post-shift, workersshowed an increase in markers.

Marth, E., F. F. Reinthaler, K. Schaf-fler, S. Jelovcan, S. Haselbacher, U.Eibel, and B. Kleinhappl. 1997. Occupa-tional Health Risks to Employees ofWaste Treatment Facililties. Annals ofAgricultural and EnvironmentalMedicine. 4:143-147.

Conclusion: Elevated IgE (a trace serumprotein [antibody] associated with allergicreactions) was detected in compost work-ers, however no statistically significant in-crease in allergic diseases was found. Sev-eral measures of allergy, inflammationand lung function were measured in 117workers at two composting and threewaste sorting facilities and comparedwith a control group. Eye and mucousmembrane irritation, coughing and de-creased lung function were measured.

Cobb, N., P. S. Sullivan, and R. A. Et-zel. 1995. Pilot Study of Health Com-plaints Associated with Commercial Pro-cessing of Mushroom Compost inSoutheastern Pennsylvania. Journal ofAgromedicine. 2(2):13-25.

Conclusion: No significant health haz-ard associated with the mushroom com-post site could be demonstrated. In re-sponse to residents’ complaints, asymptom questionnaire was adminis-tered to 100 residents living within 3,000feet (inner zone) and living between 3,000and 5,000 feet (outer zone) from a mush-room composting facility, and to two con-trol groups. Local physicians were inter-viewed and some air and water testingwere performed. Inner zone residents re-ported more symptoms than those in theouter zone, but not more than one of thecontrol groups. No statistically significantimpact on health was found.

Millner, P. D., S. A. Olenchock, E. Ep-stein, R. Rylander, J. Haines, J. Walker,B. L. Ooi, E. Horne, and M. Maritato.1994. Bioaerosols Associated with Com-posting Facilities. Compost Science andUtilization. 2(4):6-57.

Conclusion: “Composting facilities donot pose any unique endangerment to thehealth and welfare of the general public.”This paper is a review based on a work-shop. It provides a review of the litera-ture that was available in the early1990s. The conclusion is based primarilyon “the fact that workers were regardedas the most exposed part of the commu-nity and where worker health was stud-ied, no significant adverse health im-pacts were found … [and] in most casesthe measured concentrations of the tar-geted aerobic bacteria, thermophilic(heat loving) fungi, and Aspergillus fu-migatus bioaerosols in the residentialzones around composting facilitiesshowed that the airborne concentrationsof bioaerosols were not significantly dif-ferent from background.”

There were few available data onbioaerosol concentrations, particularly foryard waste composting sites. Some of thenon-yard waste studies had downwindmonitoring far away (i.e. half mile and 1mile). Slightly elevated levels of As-pergillus fumigatus at nearest monitoringstation (500 feet) downwind of compostpad (WSSC Site 2, Clayton EnvironmentalConsultants, Ltd., 1983) were detected inone study. Current data (as of early 1990s)were found to be insufficient to resolvequestions regarding the potential healthimpacts of siting a large yard waste com-posting facility in relatively close proximi-ty to neighbors. �

Ellen Z. Harrison is Director of the CornellWaste Management Institute at CornellUniversity in Ithaca, New York;http://cwmi.css.cornell.edu.