Draft Screening Assessment report of
Nitrobacter winogradsky ATCC 25391,
Nitrobacter species 18132-6,
Nitrobacter species 16969-4,
Nitrosomonas europaea ATCC 25973,
Nitrosomonas species 16968-3,
Nitrosomonas species 18133-7,
Rhodopseudomonas palustris ATCC 17001,
Rhodopseudomonas species 18136-1
Table of Contents
Pursuant to paragraph 74(b) of the Canadian Environmental Protection Act, 1999 (CEPA 1999), the Ministers of the Environment and of Health have conducted a screening assessment of eight lower-hazard (Priority C) micro-organism strains. These strains were nominated and added to the Domestic Substances List (DSL) because they were manufactured in or imported into Canada between January 1, 1984 and December 31, 1986, and they entered or were released into the environment without being subject to CEPA 1999 or any other federal or provincial legislation.
Living organisms on the DSL were prioritized into three groups (Priority A, B, C) based on known hazard characteristics. The 27 micro-organisms in the Priority C (lower-hazard) group are being assessed using an expedited approach in parallel with the more complex assessment of 13 micro-organisms in the Priority A (higher hazard) group with the objective of assessing the entire number of DSL micro-organisms more efficiently and to provide greater certainty to industries that use these microorganisms. The Priority C group was further sub-divided into four “Lots” for assessment based on their taxonomic classification (genus or species) and their known and potential uses related to their biological properties and on whether they remain in commerce in Canada. This Notice pertains to Lot 1 of the Priority C group. For more information, please refer to the document Prioritization of Micro-organisms on the Domestic Substances List prior to the Screening Assessment under paragraph 74(b) of CEPA 1999.
| Organism | Strain or Accession Number |
|---|---|
| Nitrobacter winogradskyi | ATCC 25391 |
| Nitrobacter species | 18132-6 |
| Nitrobacter species | 16969-4 |
| Nitrosomonas europaea | ATCC 25978 |
| Nitrosomonas species | 16968-3 |
| Nitrosomonas species | 18133-7 |
| Rhodopseudomonas palustris | ATCC 17001 |
| Rhodopseudomonas species | 18136-1 |
Where strain-specific data were not available, surrogate information from literature searches was used. Surrogate organisms are identified in each case to the taxonomic level provided by the source. Information identified up to January 2012 was considered for inclusion in the screening assessment report.
This screening assessment was prepared by staff in the Biotechnology Sections at Health Canada and Environment Canada. Both the human health and ecological portions of the Nitrobacter species assessment underwent written peer review by Peter Bottomley (Oregon State University), a scientist external to the government who has expertise in that organism.
Hazard assessment
The eight micro-organisms in Lot 1 are naturally occurring bacteria. None is recognized as a human pathogen by the Public Health Agency of Canada and no adverse human health effects have been associated with these strains, their genetic material, secondary metabolites or structural components. Similarly, none of these strains are recognized as animal or plant pathogens by the Canadian Food Inspection Agency or by any member country of the International Plant Protection Convention. Furthermore, an in-depth scientific literature search yielded no reports of the presence of virulence factors or evidence of toxicity or pathogenicity towards humans, plants, vertebrates, or invertebrates. These observations are supported by genomic sequencing and analysis of these strains (Starkenburg et al., 2006; Chain et al., 2003; Larimer et al., 2004). In the unlikely event of infection, all Lot 1 strains are susceptible to clinically relevant antibiotics.
The hazard potential associated with the micro-organisms in Lot 1 was estimated to be low for both the environment and human health.
Exposure assessment
The eight micro-organism strains in Lot 1 are present in a variety of natural environments, but there is little information or data on the level of exposure from these settings. The purpose of the exposure assessment is to characterize human and environmental exposure to these eight strains from their deliberate use in consumer or industrial products used in Canada.
The exposure associated with the eight micro-organism strains in Lot 1 was gathered from publicly available sources and through a mandatory information-gathering survey (Notice) under section 71 of CEPA 1999, as published in the Canada Gazette on October 3rd, 2009.Based on responses to this survey, strains in Lot 1 are used in quantities ranging from 50-200 kg per year as ingredients within commercial and consumer products. No information on Nitrobacter sp. 18132-6, Nitrosomonas sp. 18133-7, or Rhodopseudomonas sp. 18136-1 was collected through the Notice as they were nominated to the DSL after the survey took place.
Current and potential uses of Lot 1 micro-organisms are as ingredients in microbial-based products used for bioremediation, biological waste treatment, and municipal waste water treatment; to clean drains and grease traps in restaurants; and to improve water quality in commercial and hobby fish production facilities, and more. Their mode of action is based on their ability to degrade nitrogenous wastes, grease and oils, and man-made chemicals in industrial effluents (halogenated and aromatic compounds, and active pharmaceutical ingredients).
Human exposure is expected primarily through direct contact with consumer and commercial products containing these micro-organisms. For example, during the application of household products containing these strains, dermal exposure and inhalation of aerosolized droplets or particles containing micro-organisms is likely. Contact with the eyes and incidental ingestion secondary to the contamination of hands and food preparation surfaces may also occur. Intended and potential uses are likely to introduce these micro-organisms to soil and water. Human exposure through treated water, wastewater effluent or bioremediation sites is not expected to be significant, but environmental flora and fauna may come into contact with these micro-organisms when they are released from commercial, industrial or manufacturing activities.
There is little information on background concentrations of Lot 1 micro-organisms or their persistence in the environment. Nitrobacter winogradskyi has been reported to be present in soil at concentrations of 104 -105 cells per gram (Rennie and Schmidt, 1977), which is consistent with the nature of Nitrobacter winogradskyi as a slow-growing, difficult to culture micro-organism that declines quickly when introduced into environments that do not provide ideal growth conditions. No measurement of Nitrosomonas europaea concentrations in natural soil was found; however, ammonium oxidizing organisms are estimated to be present at concentrations between 105 to 106 organisms/cm³ (Lang and Elliott, 1997). Ammonia oxidizing organisms are able to survive periods of desiccation (up to 10 weeks) through polysaccharide encapsulation (Allison and Prosser, 1991). There is no information or data on survival or persistence of Rhodopseudomonas palustris populations. Based on available information and data, Lot 1 strains are not expected to persist in the environment at concentrations above background levels.
Given the range of current potential applications of these micro-organisms, and market trends towards increased use of microbial-based products instead of chemical products in certain sectors, the scale and frequency of use of these strains is expected to increase with consequently higher releases to the environment. Conservative assumptions have therefore been applied to the exposure characterization.
Therefore, the exposure associated with the micro-organism in Lot 1 is estimated to be moderate for both the environment and human health.
Risk assessment
The eight strains are not recognized to cause disease and the routes of exposure are not expected to lead to adverse environmental or human health effects.
Owing to the lack of documented evidence for adverse effects related to these strains in spite of their ubiquity in nature and taking into account the numerous intended and potential uses, the estimated risk fromhuman and environmental exposure resulting from all their known and potential uses is expected to be low for both the environment and human health.
Proposed conclusion
Based on the available information, the substances listed in this assessment are not entering the environment in a quantity or concentration or under conditions that have or may have an immediate or long-term harmful effect on the environment or its biological diversity, that constitute or may constitute a danger to the environment on which life depends, or that constitute or may constitute a danger in Canada to human life or health. It is therefore proposed that these substances do not meet the criteria as set out in section 64 of CEPA 1999.
More information on the assessment approach for lower hazard micro-organisms on the Domestic Substances List is available on the Government of Canada’s Chemical Substances Website.
References
Allison,S.M. and Prosser,J.I. (1991). Survival of ammonia oxidising bacteria in air-dried soil. FEMS Microbiol. Lett. 79, 65-68.
Chain,P., Lamerdin,J., Larimer,F., Regala,W., Lao,V., Land,M., Hauser,L., Hooper,A., Klotz,M., Norton,J., Sayavedra-Soto,L., Arciero,D., Hommes,N., Whittaker,M., and Arp,D. (2003). Complete Genome Sequence of the Ammonia-Oxidizing Bacterium and Obligate Chemolithoautotroph Nitrosomonas europaea. J. Bacteriol. 185, 2759-2773.
Lang,H.J. and Elliott,G.C. (1997). Enumeration and inoculation of nitrifying bacteria in soilless potting media. J. Amer. Soc. Horticult. Sci. 122, 709-714.
Larimer,F.W., Chain,P., Hauser,L., Lamerdin,J., Malfatti,S., Do,L., Land,M.L., Pelletier,D.A., Beatty,J.T., Lang,A.S., Tabita,F.R., Gibson,J.L., Hanson,T.E., Bobst,C., Torres,J.L., Peres,C., Harrison,F.H., Gibson,J., and Harwood,C.S. (2004). Complete genome sequence of the metabolically versatile photosynthetic bacterium Rhodopseudomonas palustris. Nat. Biotechnol. 22, 55-61.
Rennie,R.J. and Schmidt,E.L. (1977). Autecological and kinetic analysis of competition between strains of Nitrobacter in soils. Ecological Bulletins (Stockholm) 431-441.
Starkenburg,S.R., Chain,P.S.G., Sayavedra-Soto,L.A., Hauser,L., Land,M.L., Larimer,F.W., Malfatti,S.A., Klotz,M.G., Bottomley,P.J., Arp,D.J., and Hickey,W.J. (2006). Genome sequence of the chemolithoautotrophic nitrite-oxidizing bacterium Nitrobacter winogradskyi Nb-255. Appl. Environ. Microbiol. 72, 2050-2063.
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