By Kim Smiley
On the evening of August 1, 2014, 400,000 people living in the Toledo, Ohio region were told not to use or consume tap water. The water ban was imposed after higher levels of a toxin, microcystin, than were deemed safe were detected in the water supply. The water ban was lifted on the morning of August 4, but the issue may not be over since many of the factors that lead to the problem are still present.
This issue can be analyzed by building a Cause Map, or visual root cause analysis. A Cause Map intuitively lays out the cause-and-effect relationships that contributed to an issue. In order to build the Cause Map, “why” questions are asked and the answers are documented on the Cause Map.
So why were people told not to use their tap water? Microcystin is a toxin that can cause vomiting, cramps, rashes and even significant liver damage, and it was detected in the water supply at levels officials deemed unsafe. (No illnesses have been reported as a result of the toxin.) The investigation is still ongoing, but many scientists believe the microcystin came from a recent algae bloom in Lake Erie, where the area draws their water. Algae blooms in Lake Erie are relatively common, but recent weather patterns meant that this particular bloom occurred near the water treatment plants’ inlets.
Algae are always present in Lake Erie; they can reproduce rapidly and may form a bloom when conditions are conducive to growth and there is high nutrient availability. Scientists are still working to understand more about the algae blooms, but many believe that phosphorus in agricultural runoff is the main source feeding them. Phosphorus is commonly used in fertilizer and rain washes it into the lake where it may be consumed by algae. There are also other possible sources of phosphates such as cattle feedlots and leaky septic systems that need to be investigated.
While it’s tempting to over simplify this issue, it really is very complicated. There is research showing that an invasive species, the zebra mussel, may be adding to the problem by selectively consuming the non-toxic algae so that any blooms that form are more likely to be toxic. There is still debate about what exactly is causing the algae blooms to form. There are limited federal regulations in place to limit or monitor agriculture runoff and there isn’t agreement on what, if anything, should be done. There are not even federal limits on the allowable levels of microcystin in drinking water. Toledo officials used the limits set by the World Health Organization because there isn’t a federal standard.
There are many open questions and not enough answers. One of the things that we do know is that this particular algae bloom wasn’t particularly bigger or more intense than what has been normal in recent history. Its main distinguishing characteristic was the location near the water plant inlets. Scientists are predicting that blooms will peak in September this year so the impacts on the water supply may not be over for the year.