Household Hazards

How everyday products make us sick.

After the Bloom Fades

Biotoxins at play and work

A recent report from the Centers for Disease Control (CDC) underscores yet another potential emerging hazard: harmful “algal” blooms. The freshwater overgrowths the CDC detailed represent more than just repulsive surface scum. The accumulated microscopic organisms that are blooming can release biotoxins, naturally occurring, but nonetheless hazardous substances.

The CDC, ever fond of acronyms, refers to such harmful algal blooms as HABs (also turning algae into the adjectival algal) (http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6301a3.htm). Thus shortened to “HABs”, the phenomenon may sound simple and contained, but the reality is more complex and troublesome. First of all, the culprit is not familiar algae, at least in the sense of “kelp.” The blooms are due to the dense overgrowth of microscopic phytoplankton of various types. One phytoplankton group called cyanobacteria often dominates in fresh water HABs. Exposure can vary in intensity and can occur through skin contact, ingestion, or inhaling droplets (think water polo, for example). For these reasons, it is not surprising that the symptoms inked to HABs are varied and multiple. Some can mimic a non-specific acute illness such as the flu, including fever, muscle aches, and sore throat. Many times nausea, diarrhea, or other gastrointestinal complaints suggest a more mundane water-borne illness. Depending on how heavy the exposure and the mix of biotoxins (more than one can be involved), the nervous system can be affected. Inhalation of droplets can cause cough and wheezing. Moreover, it’s not just us humans on the firing line. Often, the harbinger of a bloom is a kill-off of fish or birds; family pets are also at risk.

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You may ask yourself, why haven’t I heard of this before? It’s partly because the phenomenon is not all that well understood and the reporting of outbreaks is inconsistent, in large part because of the non-specific nature of the illnesses that result. But, ominously, the problem seems to be on the upswing. According to the CDC, 14 freshwater HABs were reported in its surveillance program since 1978, but of those, 11 occurred in 2009-2010 alone (the most recent time period with reported events). The most conducive factors promoting these HABs are warm water and rich nutrients. A warming climate combined with poorly controlled industrial–scale agriculture fertilizer run-off could explain the upswing in events.

This latest CDC report emphasizes freshwater hazards, but saltwater has long been the major source for phytoplankton-derived biotoxins.  This includes a type of marine microalgae that, when it blooms, causes what is commonly known as a “red tide.” The biotoxin released in red tides (called brevetoxin), produces, among other effects, asthma-like breathing attacks in people who simply may be walking along the beach and inhaling minute amounts of toxin-laced ocean spray  (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2683400/). Some of the marine toxins are even more dangerous than those in freshwater HABs or red tide. A biotoxin called domoic acid, for example, is concentrated from phytoplankton in shellfish and certain other sea foods and is poisonous to the nervous system. In humans, it causes a syndrome known as “amnesic shellfish poisoning.” Domoic acid also can be lethal to marine mammals (in whom we can’t assess more subtle effects – it’s hard to diagnose memory loss in a seal). One marine mammal that has experienced a double-wammy of phytoplankton toxicity is the California sea otter, an endangered species threatened not only by ocean-originating domoic acid, but also from cyanobacteria-laced run-off from fresh water sources (http://otterproject.wordpress.com/).

Yet another marine biotoxin is called palytoxin. It one of the most potent, but it is also a toxin that has been hard to pin down. An obscure syndrome first reported almost a century ago is now suspected to be due to palytoxin: “Haff disease”, named not after an observant doctor called Haff, but rather a spit of land in the Baltic Sea where there first outbreak was reported. Haff disease is linked to eating certain kinds of seafood, characteristically but not exclusively bottom-feeders that presumably concentrate the toxin from phytoplankton. Haff disease is marked by severe and potentially life-threatening muscle breakdown. Outbreaks of Haff disease are sporadic, but in recent years it has, for the first time, even been reported in the United States. Unfortunately, palytoxin exposure seems to be a wider problem than consuming the wrong seafood – there is at least one other route by which this biotoxin can come into the home. A recent medical report documented two separate incidents in which illness occurred after inhaling vapors likely contaminated with palytoxin. In both events, the exposure came about through home fish tank removal of “Palythoa coral,” pouring boiling water over (to kill it) , and inhaling the steam vapors given off. The coral is not a phytoplankton, but rather is symbiotically associated with such micro-organisms (http://www.ncbi.nlm.nih.gov/pubmed/23702624). It is easy to find other, personal accounts of misadventures by aquarium hobbyists, such as Adrianne’s story of her own poisoning (in that case through an open wound) (http://www.advancedaquarist.com/blog/palythoa-toxica-poisoning-one-reefkeepers-personal-experience-with-palytoxin-poisoning).

When it comes to these hazards, individual action has a role, of course. Common sense measures include: Don’t splash around in scummy ponds, don’t stroll on the beach in the midst of red tide warnings, and certainly don’t go pouring boiling water on Palythoa coral. But without collective action, we can’t address important root causes of increasing microtoxin-caused illness, including water pollution (on land and at sea) and climate change.

Paul D. Blanc, M.D., M.S.P.H., is Professor of Medicine and Endowed Chair in Occupational and Environmental Medicine at the University of California San Francisco.

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