Xenobiotics

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Xenobiotics

• Donald R. Kendall

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Xenobiotics Defined

• Broad range of contaminants that are now being
  found in the environment. There are three
  general categories.
• Hormonally Active Agents (HAAs) Human and
  animal estrogens, Detergent residues, and Low
  volatility solvents.
• Pharmaceutically Active Compounds (PhACs)
  Prescription drugs, Non-prescription drugs, and
  Illicit drugs.
• Personal Care Products (PCPs) Disinfectants,
  Deodorants, Fragrances, Flavoring agents, insect
  repellants, sunscreens.

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Concerns

• Concerns over xenobiotics were initially raised
  in response to mutogenicity in the aquatic
  environment, but have been broadened to consider
  human health effects and pathogen resistance.
• It is believed that many of the substances have
  been present in the environment, but were not
  previously detected due to lack of sufficient
  analytical methods. ( Now being detected in the
  parts/trillion or nanograms/liter range)

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History of Xenobiotics

• 1930s Hormone mimics reported from plant and
  synthetic sources.
• 1940s Metabolites of synthetic chemicals found
  to be estrogenic.
• 1950s DDT and bisphenol A determined to be
  estrogenic
• 1965 Study on the removal of natural and
  synthetic hormones from activated sludge.

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History of Xenobiotics Cont.

• 1970s Heart medications and pain relievers
  detected in wastewater effluents.
• 1980s Oral birth control medications reported
  in natural waters.
• 1990s Various reproductive ailments in animals
  and humans attributed to endocrine disruptor
  compounds.
• 1997 Our Stolen Future by Theo Colburn
  indicates human and ecological dangers of EDCs.

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USGS Survey

• USGS did a survey of 95 Organic Wastewater
  Contaminants (OWCs), including several
  pharmaceuticals and hormones, in 139 streams
  across 30 states (including several in
  California). The survey included the use of five
  newly developed analytical methods. A copy of
  the paper summarizing the results was recently
  published in Environmental Science Technology.

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USGS Survey Results

• Results are not necessarily representative of all
  streams in the US because stream sites generally
  considered susceptible to contamination were
  selected and certain OWCs were selected because
  they had previously been identified as prevalent.
• 80 of the streams sampled had one or more of the
  OWCs. The median number of OWCs per site was
  7. The median total concentration of OWCs per
  site was 0.91 µg/l.
• 82 of 95 OWCs were detected at least once during
  the study. Those that were not detected included
  eight antibiotics and five other prescription
  drugs. Measured concentrations of individual
  OWCs were less than 1 µg/l.

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USGS Survey Results Cont.

• Only 14 of the 95 OWCs have Maximum Contaminant
  Level (MCL) or Health Advisory Level (HAL)
  standards. Of these 14, only bis(2-ethylhexyl)
  phthalate exceeded the MCL/HAL (maximum
  concentration 20 µg/l, median concentration 7
  µg/l, and MCL6 µg/l), but the exceedances were
  attributed to a single site. It was also noted
  that the concentration was estimated and that the
  compound was routinely detected in laboratory
  blanks. Two other compounds had maximum
  concentrations that exceeded the MCL/HAL
  (Dieldrin Max.21 µg/l and MCL/HAL .2 µg/l
  benzoapyrene max0.24 µg/l and MCL .2µg/l).

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USGS Survey Results Cont.

• On the basis of frequency of detection, steroids,
  nonprescription drugs, insect repellants, and
  detergent metabolites were the four most
  prevalent classes of OWCs found. Each of these
  OWCs was found in 70 or more of the sites. On
  a total concentration basis, detergent
  metabolites, steroids, plasticizers, and
  nonprescription drugs were the four highest
  ranked classes of OWCs.
• The report acknowledged that little is known
  about toxicological effects of many of the
  investigated OWCs, either individually or
  collectively. Also, in addition to the OWCs,
  some consideration must be given to their
  degradates and or select metabolites.

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Unknowns

• There is no toxicological data that would allow
  formulation of risk assessment or risk management
  alternatives.
• Relative contributions from various sources are
  unknown.
• Are there synergistic or antagonistic effects
  from one or more xenobiotic compounds?
• It has been estimated that there are as many as
  87,000 chemicals that may need to be reviewed.
• What are the economic impacts to industry and
  POTWs to reduce this risk?

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Treatment
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Treatment Methods
Conceptual Summary
Log (concentration)
RO
MF
WW Effluent
UVH2O2
Soil Aquifer Treatment
Wetlands
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Who is Responsible?

• US Food and Drug Administration require
  ecological testing of new drugs only if the
  predicted environmental concentration exceeds
  1µg/l.
• All new PhACs are tested for teratogenic (of,
  relating to, or causing malformations of an
  embryo or fetus) effects.
• US EPA has no jurisdiction over pharmaceuticals,
  but may be able to regulate them under CWA.
• USGS is developing national monitoring database,
  but has no toxicological data.

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Future Options

• Source Control
• Product substitutions/bans
• Advanced waste treatment (but where do you put
  the residuals?)
• Gather additional info for risk assessment/risk
  management
• Develop new methods of applying medicine
• Develop new products
• Public outreach (difficult to get consumers to
  change use patterns).
• ACWA has taken a position that there is
  insufficient data to determine risks. Support
  further study of occurrence, treatment, and
  potential health effects.

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Reference Websites

• http//www.epa.gov/esd/chemistry/pharma/index.htm
• http//toxics.usgs.gov/index.html
• http//www.belleonline.com/index.html