Lead has been a hot topic for consumers and the media for many years. We all have heard about the deterioration of U.S. water distribution systems, lead service lines, extremely high levels of lead in Washington, D.C.’s drinking water because of a change from chlorine to chloramine, lead in paint, lead in toys, new lead content laws in California and Vermont (soon to be national)—concerns about lead that will never go away.
Unlike many contaminants found in drinking water, lead is something that consumers have heard of. They have an idea of what it is and do not want it in their drinking water or household products. The drinking water treatment industry has responded to this demand with a variety of products that are capable of reducing lead in drinking water.
Product Testing Problems
Lead, like many heavy metals found in drinking water, can be present in different forms depending on water characteristics. Drinking water at the lower end of typical pH (6.5) usually provides a good environment for heavy metals to be found in ionic form. Lead has a positive charge at 6.5 pH. At 8.5 pH, lead in drinking water is found in two forms: ionic and particulate.
NSF/ANSI 53, the performance standard used to evaluate filtration products’ ability to reduce lead, was developed to evaluate performance at both 6.5 and 8.5 pH. This ensures products are capable of removing the two forms of lead from drinking water.
Approximately five years ago, manufacturers and laboratories were obtaining strange test results while examining products for lead reduction at 8.5 pH. After extensive evaluation, it was determined that different amounts and sizes of particulate lead were being formed in the 8.5-pH challenge water, depending on how the laboratory prepared the stock solutions and challenge tanks.
The initial attempt to solve the testing inconsistencies was the establishment of a task force to develop a stable lead 8.5-pH challenge tank, with prescribed amounts of ionic and particulate lead. This task may not seem difficult, but the task force quickly discovered that making a stable challenge tank at 8.5 pH with ionic and particulate lead was not simple.
Because the challenge tanks were not stable and the amounts of particulate lead varied from lab to lab and tank to tank, the group decided to allow wide ranges of total, fine and course particulate lead in the challenge water so that the majority of labs would be able to perform the test. The task force also agreed that the particulate lead issue should be reviewed frequently and labs should present best practices to the standards writing group to improve the protocol when possible.
Effects on the Industry
Products that relied solely on technology designed to remove lead ions from drinking water had to be re-engineered so that they could also reduce the non-ionic particulate lead from the challenge water. This presented a problem for many products that were able to pass the previous version of the standard, especially products that relied on gravity to filter water. As a result of the protocol change, many previously certified products had to drop their lead claims because of their inability to consistently pass the new lead protocol.
Third-party testing laboratories and manufacturing laboratories have been using the new protocol for several years now and new problems have surfaced. At the last NSF Intl. drinking water treatment joint committee meeting, I presented a number of issues that the Water Quality Assn. (WQA) and industry members discovered while using the lead 8.5-pH test protocol. The issues presented included:
- The lead 8.5-pH challenge tank is not stable in many labs.
- The same product may pass the testing protocol one week and fail the next week even if all challenge tank parameters are met.
- Because of analytical equipment variability and specific calculations used in the protocol, labs cannot be confident of the actual values of the fine and course particulate lead in the challenge tank.
These testing protocol issues made it difficult for companies to engineer products that consistently passed the lead 8.5-pH testing criteria. Without consistent test results, companies do not want to market a lead reduction claim.
Next Steps
WQA formed an industry task force to address the lead 8.5-pH testing protocol issues. This group was tasked to address the following concerns:
- Work with NSF’s lead task force to revise the lead 8.5-pH test protocol to address the issues WQA presented at the last joint committee meeting;
- Begin an investigation to determine the particulate lead concentrations and sizes found in drinking water sources in the U.S., and internationally if possible; and
- Present its findings to the NSF Joint Committee for consideration for the next standard revision.
WQA’s task force and the NSF lead task force, chaired by Rob Herman, have been extremely active in addressing the challenge tank stability and particulate lead challenge water content issues. Through laboratory knowledge sharing, the task forces may have a solution to the stability of the lead 8.5-pH challenge tank and may be able to tighten the range of the fine and course particulate lead tolerances. More work is needed but the group is making considerable progress.
WQA also has been working with its member companies to collect water samples from around the country to analyze them for total, ionic and fine and course particulate lead. Although WQA has received and tested hundreds of samples from around the country, the amount of lead found in the water was low, typically less than 10 μg/L. Although this was great news for consumers and municipalities, it did
not help the study.
WQA currently is working with the U.S. Environmental Protection Agency and university researchers to find drinking water with higher lead concentrations so that it can determine if the water contains high amounts of lead particulates. More work is needed, but WQA is determined to discover the prevalence of particulate lead in U.S. drinking water.
Conclusion
WQA and NSF want a performance standard that protects consumers by challenging products with reasonable worst-case drinking water. They also want to ensure that certified products reduce the drinking water contaminants claimed on the packaging. By improving the lead 8.5-pH test protocol and finding out which types of lead are found in drinking water today, they should be able to accomplish these goals. Lead in drinking water will be a major concern for consumers for years to come, and the industry needs to be able to provide solutions for these concerns.
