Grantee Research Project Results
2002 Progress Report: The Influence of Amphiphilic Molecules on the Environmental Fate and Transport of Pharmaceuticals
EPA Grant Number: R829005Title: The Influence of Amphiphilic Molecules on the Environmental Fate and Transport of Pharmaceuticals
Investigators: Kibbey, Tohren C.G. , Sabatini, David A.
Institution: University of Oklahoma
EPA Project Officer: Page, Angela
Project Period: September 1, 2001 through August 31, 2004 (Extended to August 31, 2005)
Project Period Covered by this Report: September 1, 2001 through August 31, 2002
Project Amount: $316,600
RFA: Drinking Water (2000) RFA Text | Recipients Lists
Research Category: Drinking Water , Water Quality , Water
Objective:
The overall objectives of this research project are to evaluate transport processes affecting pharmaceutical movement in the environment, with emphasis on the influence of amphiphiles (e.g., surfactants, phospholipids) on the fate and transport of pharmaceuticals in the environment. The approach involves the use of a combination of batch and column adsorption and desorption experiments involving environmentally relevant pharmaceuticals and amphiphiles. In addition, a transport simulator (tracking both surfactants and pharmaceuticals and their coupled transport) will be developed to interpret experimental results and assess the potential impact of amphiphiles on the migration of pharmaceuticals.
The specific objectives of this research project are to conduct: (1) batch adsorption/desorption experiments; (2) column transport experiments with surfactants; (3) column transport experiments with Class II amphiphiles/vesicles; and (4) development of a coupled transport simulator.
The proposed timeline for completion of these tasks is shown below:
Progress Summary:
Despite initial delays in filling
the two graduate student research positions in the first year, to date we have
been making excellent progress in Objectives 1 (batch experiments) and 2 (column
experiments), and have begun work on Objective 4 (development of a coupled
transport simulator). For our initial work, we have selected four representative
compounds from major classes of pharmaceuticals: acetaminophen (an analgesic),
carbamazepine (an antidepressant), 17--ethinylestradiol (a hormone), and nalidixic
acid (an antibiotic). The pharmaceutical compounds selected are shown in Table
1. As the project progresses, selected compounds will be added to satisfy specific
research needs.
| Acetaminophen | Class: Analgesic Molecular Formula: C8H9NO2 Molecular Weight: 151.2 |
|
| Carbamazepine | Class: Antidepressant Molecular Formula: C15H12N2O Molecular Weight: 236.3 |
|
| 17- |
Class: Hormone Molecular Formula: C20H24O2 Molecular Weight: 296.4 |
|
| Nalidixic Acid | Class: Antibiotic Molecular Formula: C12H12N2O3 Molecular Weight: 232.2 |
During the initial stages of the project, work focused on the development
of analytical methods for measuring the concentrations of these compounds.
As
anticipated, method development has been challenging, because the level of
precision needed for adsorption measurements is higher than would be needed
for analysis of environmental samples. Significant effort in the first year
was expended developing methods that had small enough error ranges to allow
high-quality adsorption isotherms to be measured. It will be possible to
detect subtle effects of surfactants and other amphiphilic molecules on adsorption
only with low-error adsorption isotherms. At present, we have developed methods
for the four compounds in Table 1, and have been conducting experiments using
these methods. As work continues, and as we examine new pharmaceutical compounds
or new surfactant components, we will continue to refine the analytical methods.
Our experiments to date have focused on studying the adsorption and transport behavior of pharmaceutical compounds in the absence of surfactants. Figure 1 shows adsorption of nalidixic acid on Canadian River Alluvium (CRA), one of the two natural materials currently being studied. The isotherm in Figure 1 is approximately Freundlich in shape. Nalidixic acid has a low aqueous solubility, and as such, adsorbs strongly to soils. For future work, we will be characterizing the solid media in terms of fraction of organic carbon and BET surface area. In addition, we will conduct selected experiments with media fractions and other model solid materials, to test hypotheses about adsorption behavior. In the second project year we will begin conducting experiments involving both surfactants and pharmaceuticals, to assess the effects of surfactants on pharmaceutical adsorption/desorption.
Figure 1. Adsorption of Nalidixic Acid to CRA.
Figure 2 shows a breakthrough curve for transport of nalidixic acid through a packed column containing F-95 sand (U.S. Silica, Ottawa, IL). Although F-95 sand has a very low organic carbon content, measurable retardation is observed (the midpoint of breakthrough does not occur until approximately 1.8 pore volumes). Also, substantial nonequilibrium adsorption behavior is observed, as the outlet concentration is only gradually approaching the inlet concentration (C/C0=1.0) with increasing pore volumes. Future transport experiments will be conducted with both CRA and the F-95 sand, and with a range of pharmaceutical and surfactant compounds.
Figure 2. Transport of Nalidixic Acid Through F-95 Sand.
The transport of low solubility compounds (such as nalidixic acid) is most likely to be accelerated by the presence of surfactants, which may interfere with adsorption or increase their affinity for aqueous solution. Conversely, the transport of high solubility compounds (such as acetaminophen) is most likely to be hindered by the presence of surfactants. Work conducted during the second project year should provide quantitative information regarding the influence of surfactants on transport of various pharmaceuticals in natural systems.
In addition to batch adsorption and transport experiments, we have begun work developing our transport simulator. Because the transport of surfactants is likely to influence the adsorption and movement of pharmaceutical compounds, a transport simulator is being developed to model the linked transport of surfactants and pharmaceuticals. Observed adsorption trends from batch and column experiments will be used to select appropriate adsorption models for various classes of pharmaceutical compounds in the presence of different surfactants.
Preliminary results from the first project year are described above. Ultimate results of this project will provide information to allow assessment of the extent to which trace levels of surfactants in the environment may influence the transport of pharmaceutical contaminants. A quantitative understanding of pharmaceutical transport in the environment will allow for more quantitative site-specific assessments of risk to human health and the environment.
Future Activities:
We will continue conducting experiments as described above, following the plan outlined in the original proposal. In the second project year, we anticipate collecting considerable data with a wide range of surfactant/pharmaceutical combinations. We also will continue work on the transport simulator, and also will begin work with Class II amphiphiles.
Journal Articles:
No journal articles submitted with this report: View all 14 publications for this projectSupplemental Keywords:
pharmaceuticals, surfactants, surface active agents, amphiphiles, subsurface transport, environmental fate, ecosystems protection, environmental exposure and risk, waste, water, wastewater, analytical risk, ecological effects, human health, ecological indicators, ecosystem, assessment, indicators, environmental chemistry, groundwater remediation, health risk assessment, hydrology, exploratory research, environmental biology, amphiphile molecules, antibiotics, anticeptris, chemical contaminants, degradation, drinking water system, drinking water contaminants, ecological exposure, exposure, fate, fate and transport, groundwater, hormones, human health effects, mobility, pharmaceuticals, pharmacokinetics, runoff, surfactants, transport, treatment, wastewater discharges, wastewater systems, wastewater treatment plants., RFA, Scientific Discipline, Ecosystem Protection/Environmental Exposure & Risk, Water, Waste, Health Risk Assessment, Fate & Transport, Ecosystem Protection, Environmental Chemistry, Ecosystem/Assessment/Indicators, Analytical Chemistry, Wastewater, Ecological Effects - Environmental Exposure & Risk, Ecological Effects - Human Health, Hydrology, Drinking Water, anticeptics, wastewater systems, treatment, antibiotics, hormones, wastewater discharges, chemical contaminants, amphiphilic molecules, pharmacokinetics, wastewater treatment plants, pharmacuticals, fate, groundwater, drinking water system, drinking water contaminants, fate and transport, pharmaceuticals, water treatment, exposure, ecological exposure, other - risk assessment, human health effects, degradation, transport, mobility, surfactants, runoffProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.