No information was available regarding actual releases of these substances from manufacturing or formulation of the pharmaceuticals. Data, however, were available to estimate the amount of each substance sold to hospitals and pharmacies for prescription across Canada for the years McLaughlin and Belknap , and MIDAS Appendix B. A conservative industrial release scenario was used to determine whether there is a potential ecological risk associated with these 20 substances when released to water via industrial releases as mentioned above, the three substances no longer registered for use as pharmaceuticals in Canada are not being examined further.
This is conducted by comparing the conservative predicted environmental concentration PEC in the aquatic environment with a predicted no-effect concentration PNEC. The result is a risk quotient RQ based on an industrial non-site-specific scenario. This simple model represents a point source discharge from an industry, its dilution in a small watercourse and calculation of a risk quotient for that scenario.
This PEC aq value is then used to calculate a risk quotient, as shown in the following equation:.
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The calculated RQs for all substances were less than 1 see full results in Appendix C. Given that the industrial scenario provides a conservative estimate of exposure, these results indicate a low potential for ecological harm to the aquatic environment resulting from local exposure from a point source industrial release. A down-the-drain release from pharmaceutical use scenario was employed to estimate the potential concentrations in multiple water bodies receiving wastewater treatment plant effluents to which pharmaceutical products containing the substances may have been released based on conservative assumptions regarding the amount of chemical used and released by consumers Environment Canada b.
These estimates are made for approximately release sites, which account for most of the major wastewater treatment plants across Canada. Although the default values are recognized to be highly conservative, if indication of risk is low based on these assumptions, further refinement of input values is not required at this time.
In light of uncertainty relating to the identity and environmental stability of the metabolites of these substances, a conservative environmental concentration value was obtained by not considering human metabolism in the derivation of the PECs. RQs were calculated using maximum PECs calculated from down-the-drain releases of these substances from pharmaceutical use and PNECs as identified during the categorization process, derived using an application factor of to account for uncertainties associated with the values.
Pharmaceuticals in Water
The maximum RQ was less than 1 for all of these substances see full results in Appendix C , indicating a low potential for ecological harm to the aquatic environment resulting from down-the-drain releases from consumer uses. Concentrations measured in various media, wastewater effluent, surface water, groundwater and drinking water including bottled water were examined, and the information available is consistent with the predicted concentrations from the models.
A comparison of the measured values with the PNECs determined for these substances results in RQs that are all less than 1, contributing to the weight of evidence indicating that there is no significant potential for ecological harm to the aquatic environment from these substances. Given the lack of exposure to these substances, no further collection or analysis of information relevant to the persistence, bioaccumulation and inherent toxicity to non-human organisms of these substances has been conducted beyond what was done for categorization.menbaldciverve.tk
Removal of Pharmaceuticals during Drinking Water Treatment | Environmental Science & Technology
Therefore, the decisions made on the hazard properties during categorization remain unchanged in this assessment. Accordingly, none of the substances are considered to meet the criteria for persistence or for bioaccumulation potential as set out in the Persistence and Bioaccumulation Regulations of CEPA Canada Drugs containing these substances as ingredients were previously assessed under the Food and Drugs Act Canada with respect to their safety, effectiveness and quality.
Only a portion of pharmaceuticals used would be released into the wastewater system. The concentration in the water source is also significantly reduced via dilution, as the waste is released into waterways. Measured data for 18 of these substances were identified for Canada and elsewhere and are shown in Appendix D. Concentrations measured in wastewater effluent, surface water, groundwater and drinking water including bottled water were examined. Overall, the studies indicated that the concentration of pharmaceutical measured decreases significantly as the substance moves from the wastewater treatment plant effluent into surface water and then the surface water is treated for drinking water purposes.
As there is variability in the use of pharmaceuticals in different countries due to different population levels, prescription preferences, drug registrations, etc. They can, however, account for releases from all potential sources and for potential reductions in drug concentrations resulting from metabolism, environmental degradation, removal via wastewater treatment, removal via drinking water treatment, etc.
For these reasons, in this case, the measured concentrations are preferable to modelled concentrations, even if measurements were made in other countries. Selection of the most relevant data was based on location of the sampling and the relevance of the media to human exposure. Canadian data were given preference over data from other countries, as they are considered to be most representative of potential exposures of Canadians.
Drinking water was considered the most relevant medium, followed by surface water or groundwater, wastewater treatment plant effluent and hospital effluent. If multiple relevant concentrations were available for a particular source e. For the two substances for which no measured data were identified, conservative assumptions were used when estimating the potential indirect exposure of the general population. It was also assumed that none of the pharmaceutical was removed through wastewater treatment or drinking water treatment processes and that there was no environmental degradation of the substance.
It is recognized that these assumptions are highly conservative; however, if indication of risk is low based on these assumptions, further refinement would not be required. Down-the-drain releases to surface water were modelled using the down-the-drain releases from pharmaceutical use scenario, as described in the ecological exposure section, and maximum PECs can be found in Appendix C.
This scenario estimates concentrations in approximately waterways across Canada. The highest values estimated by this model are typically in small waterways with low dilution capacity, which are unlikely sources of drinking water. As a result, this scenario would be expected to overestimate actual concentrations in drinking water. The estimated upper-bounding intakes of these pharmaceuticals by the general population were represented by formula-fed infants 0—6 months of age, which is estimated to be the most highly exposed age class, on a body weight basis, of those examined.
The equation for deriving the estimated intake is given below:. The estimated intakes for 18 substances with measured concentrations are presented in Appendix E, and intakes for 2 substances with only modelled concentrations are presented in Appendix F. Estimated intakes for all substances were low and range from 1. Since the majority of the measurements were based on wastewater treatment plant effluent or surface water, it is expected that these estimates provide conservative upper-bounding estimates of possible exposure and that actual exposures would be significantly lower.
This determination is further supported by consideration of two additional lines of evidence for evaluation of the potential for harm to human health. A comparison was made between the range of estimated intake values for this group of 20 substances and the threshold of toxicological concern TTC value of 2. For all 20 substances, estimated intakes are in the range of or below the TTC. Although the TTC may not be applicable to every member of this group, it does provide a reference point against which the range of estimated intakes can be compared. TTC values, which are derived using probabilistic approaches, establish generic human exposure threshold values below which it is expected that the probability of adverse effects is low.
A TTC value of 0. Additional higher TTC values have been established for substances not containing similar structural alerts Munro et al. A second comparison was also made to evaluate potential risk. The lowest therapeutic dose LTD for each substance was identified, and a margin of exposure MOE was calculated to determine the ratio between the upper-bounding estimate of intake by the general population and the dose that would be expected to produce a pharmacological effect.
This approach is consistent with methodology described elsewhere Webb et al.
The LTD is the lowest concentration that evokes a desired therapeutic effect among target populations and is equivalent to the lowest dose prescribed or recommended, taking into account the number of doses per day WHO These values are derived from an assessment of the balance between safety and efficacy. LTDs were identified for each pharmaceutical by examining the dosage and administration guidelines presented in the product monographs submitted to Health Canada as part of the pre-market drug authorization, which are available from the Health Canada Drug Product Database DPD Given the very conservative nature of the exposure inputs and the use of human data to derive a point of departure for risk characterization, these MOEs support the determination that risks from indirect exposure to these substances are low.
There is uncertainty regarding the estimation of exposure due to the lack of data on concentrations in Canadian surface water or drinking water for many of these substances. However, confidence is high that actual exposures would be lower than the ones presented from the measured data and models used. However, it is unlikely that potential exposures were underestimated. Potential general population exposures to these substances could occur via other sources, such as ingestion of fish or swimming in waters where the pharmaceuticals are present, but these exposures are expected to be much less than the exposure through drinking water and so are not considered in this assessment.
Some of these substances may have additional off-label or veterinary uses that are not considered in this assessment. The quantities of the substances being used for these purposes are unknown, and so estimation of releases is not possible at this time. For the substances which have measured environmental concentrations these releases may be reflected in those measurements,. It is recognized that the LTD represents an exposure level at which a desired pharmacological response is achieved and further that at this exposure level, adverse effects, in addition to intended effects, may occur in some patients.
For certain indications and certain classes of drugs, the nature of these unintended effects may be significant. However, the LTD is developed for patients who require treatment for a particular illness and therefore are likely to be more susceptible to potential effects than a healthy individual.
Although the use of the LTD provides a tier 1 type of assessment that does not utilize all the toxicity data that may be available for each substance, the highly conservative exposure defaults that have been used lead to significant MOEs between the LTD and the estimated intakes. Considering all available lines of evidence presented in this screening assessment, there is low risk of harm to organisms and the broader integrity of the environment from these 23 substances.
It is concluded that these 23 substances do not meet the criteria under paragraphs 64 a or b of CEPA as they 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 or that constitute or may constitute a danger to the environment on which life depends. Based on the information presented in this screening assessment, it is concluded that these 23 substances do not meet the criteria under paragraph 64 c of CEPA as they are not entering the environment in a quantity or concentration or under conditions that constitute or may constitute a danger in Canada to human life or health.
Fate of Pharmaceuticals in the Environment and in Water Treatment Systems
Apotex Inc. Product monograph for Apo-Zidovudine. Product monograph for Apo-Azathioprine. Ozone oxidation of oestrogenic active substances in wastewater and drinking water. Water Sci Technol 58 2 — Baxter Corporation. Product monograph for Procytox. Pharmaceuticals and endrocrine disrupting compounds in U. Environ Sci Technol — Investigation of drugs of abuse and relevant metabolites in Dutch sewage water by liquid chromatography coupled to high resolution mass spectrometry.
Chemosphere — Environ Pollut 6 — Bristol-Myers Squibb. Product monograph for CeeNU. Bristol-Myers Squibb Canada. Product monograph for Coumadin. Product monograph for Vumon. Pharmaceutically active compounds in Atlantic Canadian sewage treatment plant effluents and receiving waters, and potential for environmental effects as measured by acute and chronic aquatic toxicity.
Environ Toxicol Chem 25 8 — Occurrence and fate of the cytostatic drugs cyclophosphamide and ifosfamide in wastewater and surface waters. Environ Sci Technol 40 23 — Therapeutic dose as the point of departure in assessing potential health hazards from drugs in drinking water and recycled municipal wastewater.