June 15, 2010 (Vol. 30, No. 12)
Estelle Riché Ph.D. Senior Scientist Millipore SAS, France
Maricar Tarun, Ph.D.
“Emerging Contaminants” from the Tap Pose Subtle Threat to Experimental Data
When the Associated Press published results from its five-month study on the presence of pharmaceuticals in drinking water in 2008, it made headlines across the country. Drugs such as antibiotics, anti-convulsants, mood stabilizers, and cholesterol-lowering medications were found to be present in the drinking water of more than 40 million Americans.
Previous studies conducted by the U.S. Geological Survey found an average of 20 different drugs in the wastewater streams they examined—everything from caffeine to over-the-counter medications, such as ibuprofen, to rare but potent cancer chemotherapy drugs.
In addition to pharmaceuticals, contaminants such as perchlorates, pesticides, herbicides, endocrine-disrupting chemicals (EDCs), brominated flame retardants, and personal-care products have also been detected in the water supply.
Despite being referred to as “emerging contaminants,” many of these compounds have been in use for decades and their presence in water is not new. What is new, however, is our ability to measure the contaminants that exist in our water supply at very low concentrations.
While such contaminants can be found in drinking water, should they be a concern for researchers? Are these contaminants making their way from the tap into the high purity water used in the laboratory?
Analytical laboratories assessing and monitoring the presence of such emerging contaminants must ensure their laboratory water is purified to the highest degree possible, so that even minute amounts of contaminant in the purified water do not interfere with trace level analyses. Other laboratories that require a similar standard of water purity are those focusing on toxicity testing and those developing the increasingly sensitive methods for the detection of emerging contaminants and their metabolites in various matrices.
But what about life science research? Does the presence of such contaminants influence the cell-based and biological assays routinely conducted in research labs? These are difficult questions to answer. The effects of these contaminants on experimental outcomes may be so subtle that the cause of unexpected results might not be immediately traced back to the water.
Emerging contaminants can be organic molecules or ions, and they can affect experiments even if they are present in the laboratory water in very small amounts. For example, mass spectrometry is widely used in analytical and life science laboratories. This technique requires extremely pure reagents and solvents, including water, to avoid contamination of ionization chambers and interferences in mass analysis.
Another example is reversed-phase HPLC. Organic contamination of water in the mobile phase is known to cause baseline shifts and the appearance of extraneous peaks that can interfere with the spectral identification and quantitation of low-level analytes.
With DNA microarrays, the presence of organic compounds and ions in the water can hinder hybridization and interfere with the detection and measurement of genes using fluorescence. Such contaminants may also affect cell culture experiments by affecting cell growth and function or cloning efficiency.
While the presence of trace amounts of emerging contaminants may not currently be an issue in most laboratories, all researchers should remain mindful of how water quality may impact experiments. If a lab’s water-purification system is not functioning properly or is incapable of removing harmful contaminants, experimental results are likely to be affected.
Many companies now monitor reports of emerging contaminants. They assess whether these contaminants are effectively removed by water-purification systems or perhaps require additional purification steps. A recent example is EDCs, which are natural and synthetic substances that alter the function of the endocrine system and consequently cause adverse effects in an organism or its progeny.
Substances suspected of being EDCs include organohalogens (chloroform, dioxins), chemicals used in pesticides (DDT), and plastics (bisphenol A, phthalates). Research groups are actively designing sensitive analytical methods to identify, quantify, and study the effects of EDCs in humans and animals. For these laboratories, high-purity water is a requirement.
In addition to EDCs entering laboratory water from the tap, the materials used in the water-purification system itself may contaminate water due to the leaching of EDCs from plastic materials in filtration membranes, resin housings, and piping. To ensure that EDCs are completely removed from laboratory water, a point-of-use cartridge can be used.
It is critical that awareness of both emerging and well-known contaminants remain high for both developers of laboratory water-purification systems and researchers. New contaminants will certainly be identified and may require novel purification techniques, while concentrations of known contaminants that currently do not pose a concern for most laboratories may rise to levels that have a widespread impact on analyses and experimentation.
Posing a further challenge is the increased sensitivity of analytical methods. As methods become more sensitive, the likelihood that existing contaminants may become increasingly detectable and interfere with, or confound, results also increases. These methods—HPLC, LC-MS, PCR, and microarrays, just to name a few—all share the requirement for one critical reagent—water. Used as blanks, for dissolution and dilution of samples, dilution of standards, preparation of mobile phases and for media and buffer preparation, water is central to a laboratory’s productivity and success.
Purified water is one of the most common reagents in the laboratory—used throughout experimental protocols in virtually every type of application. The emergence of new contaminants, and our ability to detect existing contaminants in water at extremely low levels, require us to ask an important question: Do you know what’s in your laboratory water?