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2.3. Evidence for Ecotoxicity (Ruhoy)
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2.3. Evidence for Ecotoxicity (Ruhoy)

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By Ilene Ruhoy.

By Ilene Ruhoy.

This slidecast is part of the GreenPharmEdu.org program.

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    2.3. Evidence for Ecotoxicity (Ruhoy) 2.3. Evidence for Ecotoxicity (Ruhoy) Presentation Transcript

    • Evidence for Ecotoxicity
      GreenPharmEdu.org
    • Effects on Aquatic Organisms: Cause for Concern
      “Pseudo-persistence” of APIs
      Continuous, multigenerational exposure
      May be endocrine disruptors
      alterations to sexual differentiation
      Boulder Creek (feminization)
      Potomac River (intersex)
      reproduction and growth impairments
      Antidepressants and frogs
      subtle, behavioral effects
      More questions than answers about effects of APIs on aquatic species and the possibility of chronic effects in sensitive subpopulations of humans
      Little is known regarding bioconcentration
    • 1st National Survey* Revealed Extent of PPCPs in Waterways
      USGS “Reconnaissance” study in 1999-2000 was 1st nationwide investigation of pharmaceuticals, hormones, & other organic contaminants:
      139 streams analyzed in 30 states
      82 contaminants identified (many were pharmaceuticals)
      80% streams had 1 or more contaminant
      Average 7 contaminants identified per stream
      Since 1998, peer reviewed papers on PPCPs have increased from fewer than 200 per year to greater than 1,000 per year
      * KolpinDW,et al. "Pharmaceuticals, hormones, and other organic wastewater contaminants in U.S. streams, 1999-2000: a national reconnaissance." Environmental Science & Technology 2002, 36(6):1202-1211; doi:10.1021/es011055j
    • APIs as Environmental Contaminants
      Questions remain regarding:
      (i) low-dose effects – the potential for biological effects (especially in non-target organisms) from APIs at levels far below therapeutic levels, and often at levels below traditional no-observed-effects-thresholds (NOELs).
      (ii) interactive effects – resulting from simultaneous (or sequential) exposure to multiple (or multitudes of) APIs, including additivity (from APIs sharing the same mechanism of action) and synergism or potentiation.
      (iii) exposure timing – during critical windows of vulnerability, which can range from particular developmental lifecycle stages to particular periods of a daily biorhythm (chronobiology).
      (iv) exposure duration – chronic exposure sustained during a lifetime or even over multiple generations.
    • APIs as Environmental Contaminants
      Exposure to chemical stressors encompasses all chemicals - not just APIs. These unknowns are greatly magnified when other chemicals are factored into exposure scenarios.
      These include
      not just anthropogenic/synthetic compounds,
      but also naturally occurring xenobiotics, especially those present in foods (e.g., toxicants produced by plants and microorganisms).
      Adding yet further complexity is simultaneous exposure to countless other, non-chemical stressors.
    • APIs as Environmental Contaminants
      The importance of filling these gaps in toxicology becomes clear when considering the basics of what is known regarding the occurrence of APIs in the environment - in ambient waters, drinking water, and the tissues of fish and plants.
      API occurrence in these compartments clearly poses concerns regarding exposure for non-target biota - organisms for which APIs were generally never designed or intended.
      Analogous concerns pertain to human exposure, not just via drinking
      water, but also via the diet in the form of contaminated biota especially fish and plants.
      The concerns surrounding human exposure focus on those for whom exposure should be avoided as well as for those who are exposed without their knowledge.
    • APIs as Environmental Contaminants
      Much of the earlier work on APIs in the environment focused on identifying and measuring APIs in various environmental compartments and in studying the removal of APIs by STPs.
      Only more recently have efforts begun to focus on non-target organism exposure and biological effects
    • APIs as Environmental Contaminants
      Comparatively few of the APIs in current use have been evaluated.
      The maximum API levels known to occur in the aquatic environment tend to be in the ppb-range (micrograms per liter, which is roughly the nM range for conventional small-molecule APIs).
      The numbers of APIs to which aquatic organisms are known to have been exposed simultaneously are roughly a dozen.
    • APIs as Environmental Contaminants
      Kolpin et al. reported the simultaneous presence of multiple APIs in the first large-scale monitoring of streams in the U.S.
      This means that if many APIs are present and share the same mechanism of action (MOA), then the dose is effectively summed accordingly (known as dose additivity).
      For APIs known to occur in the environment, examples of drug classes whose individual APIs share the same MOA include estrogens, SSRI antidepressants, NSAIDs, specific classes of antibiotics (e.g., sulfa drugs), and statin lipid-lowering agents.
    • APIs as Environmental Contaminants
      Monitoring studies are less common for fish having APIs concentrated in various tissues; this is largely because of the difficulty in analysis of trace levels in these difficult matrices.
      The first compilation of the published fish-tissue data is available from Daughton and Brooks
    • APIs as Environmental Contaminants
      Even when multiple APIs are targeted in fish monitoring, the number present at the same time in any one fish total fewer than a half-dozen; for example, diphenhydramine, diltiazem, carbamazepine, and norfluoxetine have been reported simultaneously in the same wild fish by Ramirez et al.
      The concentrations across tissues vary by many orders of magnitude as a function of the species and specific tissue, with bile often serving to concentrate the most (commonly in the mg/kg range) and the brain the least (µg/kg and lower).
    • APIs as Environmental Contaminants
      The exposure scenario posing the most uncertainty regarding toxicology is long-term exposure to multiple APIs - with some having different MOAs and with each being present at an ultra-low level (e.g., ng/L).
      The outcomes that might be expected in the aquatic environment are usually expected be subtle such as alteration of behavior, rather than more obvious effects endpoints such as growth or survival.
      One example is reduction in activity or alteration in behavior of aquatic organisms when exposed to trace levels of APIs such as SSRIs or NSAIDs
      alterations in avoidance or attraction can change predation and reproductive behaviors , thereby effecting change in ecological community structure.
      The exposure levels at which these types of effects can be measured can be up to 6 orders of magnitude lower than the existing NOELs for conventional endpoints.
      For highly potent APIs, profound effects can occur at low ng/L levels; the adverse effect of ethynylestradiol on fish populations is one example