While safe drinking water is a major focus for public health officials and researchers, scientists are also working to determine other ways that harmful algal blooms and the associated toxins—in particular microcystin—may impact human health. In this focus area, science teams develop techniques to better detect toxins in biological samples, study the effects of algal toxins on various types of cells, and determine the significance of the different ways that people might be exposed to algal toxins—physical contact, eating fish, etc. These studies aim to assist agencies as they develop guidelines for handling harmful algal blooms in coming years.
Method Development for Detecting Toxins in Biological Samples
Researchers at the University of Toledo have developed a method to detect microcystin compounds in human tissue. Since harmful algal blooms are a relatively recent issue, scientists are still developing the tools needed to tell whether algal toxins or their byproducts remain in the tissue of plants, animals or humans exposed to them. Accurately measuring these toxins in urine, blood and human tissues is a necessary first step in understanding the ways in which these substances might be hazardous to health.
The team has refined a laboratory method to measure how much of the family of algal toxins of greatest concern — the microcystins — can be found in the human body. They’re using a technique called liquid chromatography-mass spectrometry that is able to separate and quantify several different forms of microcystin as well as the related compounds that result when the body breaks them down.
Currently, the researchers are able to quantify microcystins in concentrations between 1 ppb (part per billion, a measure of toxin concentration in water) and 100 ppb.
Drinking water advisories are generally issued at 1.6 ppb, and no contact with contaminated water is recommended at concentrations above 6 ppb.
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Fish Flesh and Fresh Produce as Sources of Microcystin Exposure to Humans
Stuart Ludsin, The Ohio State University
Microcystin, one of the major toxins produced by harmful algal blooms, has been implicated in a number of health issues, from skin rashes to liver and nervous system damage. A main focus of preventing these negative health impacts has been limiting exposure to contaminated water, but researchers at The Ohio State University have been looking at things from a different angle: microcystin exposure from food.
Lake Erie fish like walleye and yellow perch often swim through algal blooms, absorbing potentially contaminated water through their gills and eating up smaller animals that in turn may have been exposed to toxin. Likewise, vegetable crops watered with water from a source with harmful algal blooms may also be at risk for accumulating toxin in the edible parts of the plant.
Researchers have examined whether fish actually retain the algal toxin they are exposed to, and whether those concentrations are high enough to be of concern. Although results have shown that in both cases there is some toxin accumulation, findings support the current Ohio Environmental Protection Agency (OEPA) general guideline of eating no more than one fish meal per week from any Ohio water body.
The researchers developed a procedure to use liquid chromatography tandem-mass spectrometry (LC-MS/MS) with the fish samples, as that method has been shown to offer more reliable results than the current testing method. With help from Ohio State’s Food Innovation Center, the scientists are now able to quantify nine different types of algal toxins from fish tissue samples, including some of the most abundant and toxic forms of microcystin.
They’ve already used that procedure to process fish samples from Lake Erie and Grand Lake St. Marys for OEPA and the Ohio Department of Natural Resources. Results show that in the few fish that showed detectable levels of microcystin in edible tissues, which don’t include the liver and other organs, those levels were still well below consumption limits.
With one lab focused on analyzing fish samples, another laboratory team grew three types of vegetables — lettuce, carrots and green beans — while watering them with microcystin-contaminated water at different concentrations. After harvest and testing, they found that green beans accumulate more toxin than carrots, both accumulate more toxin than lettuce, and more toxin accumulates in the roots than the leaves.
In addition to toxin accumulation in both plants and the soil surrounding them, the team found that microcystin exposure can stunt plant growth, distort shape and cause yellowing, making the vegetables less valuable as commercial crops. To avoid these issues, the researchers suggest regular water testing and finding an alternative source of water for irrigation if elevated toxin levels are found. If the toxin is found in soil, rotating cropland gives the toxin time to degrade before planting new crops. At the moment, this isn’t much of a concern for Ohio crops because most farms use groundwater for irrigation, but it’s valuable information in other areas of the world, where farmers may not have that option.
Based on these results, OEPA has also been investigating the potential for microcystin to accumulate in water treatment plant residuals — what’s left over after clean water is sent back to consumers — and can limit use of those residuals as fertilizer if that is the case.
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Evaluation of Cyanobacteria and Their Toxins in a Two-Staged Model of Hepatocarcinogenesis
Christopher Weghorst, The Ohio State University
Illnesses caused by exposure to cyanobacterial toxins, which come from harmful algal blooms, are well known. That’s especially true for microcystin, the cyanobacterial toxin that led to a drinking water ban in Toledo in 2014.
For those who drink the water, symptoms range from skin irritation to stomach cramps, vomiting, nausea, diarrhea, fever, sore throat, headache, muscle and joint pain, blisters of the mouth and liver damage. Those who swim in the water may suffer from asthma, eye irritation, rashes, and blisters around the mouth and nose.
While cyanotoxins have been suspected by the International Agency for Research on Cancer to be cancer-causing in humans, what researchers don’t know for sure is how carcinogenic, or cancer-causing, the toxins might be.
Enter scientists in the College of Public Health at The Ohio State University. Their pilot research project examined whether chronic exposure to drinking water containing microcystins as well as other components in cyanobacteria increases liver cancer development in mice.
Results indicate that chronic exposure to drinking water containing algal toxins, at concentrations at or near recreational water exposure limits, could be connected to a promotion of liver cancer development, especially in organisms with a genetic predisposition to cancer.
While chemically-initiated mice exposed to algal toxin-containing drinking water did not develop significantly higher numbers of liver tumors than those exposed to clean drinking water, the tumors that did form in the livers of mice ingesting the toxins were more advanced. The researchers plan to continue this research via a larger proposal submitted to the National Institutes of Health.
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Characterization of Recreational Exposures to Cyanotoxins in Western Lake Erie Basin
While human exposure to harmful algal bloom toxins via drinking water is a major area of research, not much attention has been paid to recreational and work exposure through fishing, swimming or boating. Researchers at the University of Toledo surveyed recreational water users and those who work on or close to Lake Erie to determine when, where and how potential exposures may be occurring.
The researchers received 327 survey responses from recreational users who may be exposed to cyanotoxins through swimming or boating. The group is solidifying sampling methods for airborne exposure to aerosolized microcystin through a related project funded by the University of Cincinnati, and they have about 150 potential subjects for more detailed surveys in the future. They also have commitments from groups that represent those who work on or close to the lake—charter boat captains and fishing boat crew, for example—to participate in data collection on occupational exposure via air sampling on some of their boats.
These surveys prepared the research team for future funding, where they will examine the health impacts from recreational and occupational exposure to cyanotoxins. They’ll also measure aerosolized microcystin, which comes from harmful cyanobacteria caught up in the water spray that waves create. The end goal is to connect those exposures to any self-reported health impacts, such as skin rashes, liver problems and respiratory issues, which are common examples of health effects caused by cyanotoxins.
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A Comprehensive Approach for Evaluation of Acute Toxic Responses After Microcystin Ingestion
Ingesting microcystin toxin can have acute negative effects on the liver and other organs. However, most studies of these effects have been done in mice via injection of toxin into the belly. This research aims for a more realistic approach to microcystin exposure by giving the mice toxin via a feeding tube to better understand and treat those effects on humans in the future.
After a literature review that suggested a very wide range of toxin dosages for the experiments, the researchers have completed a preliminary study to decide on three dosages: 5,000 micrograms of microcystin per kilogram of body weight per day, as well as 3,000 micrograms and a toxin-free control group. This main study is currently under way, using both male and female mice to detect any sex-based differences.
Study results will form a foundation for future research into the effect of microcystin on the liver, giving researchers a method of oral toxin exposure that more closely mimics human exposure.
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Impact of Microcystin on Pre-Exisiting Liver Disease
Microcystins, the toxin group produced by harmful algal blooms in Lake Erie, are known to negatively affect the liver, nervous system and skin. Other HABRI projects are focusing on whether that liver damage includes an increased cancer risk, while this project focuses on non-alcoholic fatty liver disease (NAFLD), the most common liver disorder in the United States.
Criteria for healthy exposure limits to algal toxins were developed based on healthy animal models, without existing liver problems, so the implications of these toxins for all types of patient populations are not well understood. The researchers used laboratory mice bred to exhibit symptoms similar to NAFLD and exposed them to what is considered a low toxin dose with no observable health effects.
Results showed an increase in liver damage in the treated mice, suggesting that further research may be needed to evaluate current exposure limits (in drinking water as well as through recreational water use) specifically for populations with existing liver disease. The findings also offer a baseline for additional research into diagnosing microcystin exposure and developing effective therapies for the consequences of microcystin toxicity in these vulnerable patients.
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Development of the MMPB method for quantifying total microcystins in edible fish tissues
Stuart Ludsin, The Ohio State University
Microcystins, a group of toxins produced by harmful algal blooms, have been implicated in a number of health issues, from skin rashes to liver and nervous system damage. Contaminated water is implicated in most cases of toxin exposure, but researchers are also looking into eating lake fish as a possible exposure pathway.
Building on previous fish research described in this report, scientists are now working with a testing method called MMPB to quantify total microcystin in tissue samples, to complement a previously developed method called LC-MS/MS that detects specific types of microcystin. That approach allows agencies like the Ohio Environmental Protection Agency to issue any needed drinking water or fish consumption warnings based on a conservative estimate of potential toxicity, while the more detailed analysis by type offers information specifically about some of the most toxic forms of microcystin. Both techniques are more labor-intensive, but tend to be more accurate and less prone to false positives than the ELISA method that is currently used in most agency labs.
So far results have shown that there is some toxin accumulation in Lake Erie fish (the study is testing walleye, yellow perch and white perch), but no reason to completely avoid consumption as long as people follow the Ohio Department of Health guideline of no more than one Ohio-caught fish meal per week. The researchers continue to improve their procedure, and aim to finalize it during the summer of 2017.