Harmful Algal Blooms (HABs) affect the quality of fresh and marine waters and adversely
affect both animals and humans. Public health risks include exposure to toxins through
consumption of contaminated drinking water and fish and shellfish, and by recreating
on or in contaminated waters. Federal and State professionals and researchers contributed
to this Special Issue on HABs and Public Health with research papers and reviews on
various aspects of public health including the occurrence and fate of toxins in the
environment, monitoring efforts in freshwater and marine water systems, human health
risk assessment, effectiveness of treatment techniques, and guideline development.
Understanding the processes cyanobacteria and their toxins undergo in the environment
is considered in the papers by Schmidt et al. [1], Fadel et al. [2], and Song et al.
[3]. Schmidt et al. [1] discussed the environmental fate of microcystins, cyanobacterial
toxins, and their toxicokinetics (absorption, metabolism, distribution, and excretion)
in the body. Regarding environmental fate, the authors not only discussed the process
of photodegradation of microcystins, but also the contribution of bacterial degradation
that transforms the parent compounds into a series of conjugated products. This detoxification
process, which according to the authors, is not well understood, could form toxic
conjugates. Toxin degradation is also considered in the paper by Fadel et al. [2].
The authors recorded the degradation of cylindrospermopsin, another cyanobacterial
toxin, due by sedimentation in lakes or by degradation, even in the presence of cylindrospermopsin-forming
cyanobacterium blooms. This research emphasized that although it was not possible
to definitely determine the relationship of cylindrospermopsin with other environmental
factors, such as nutrients, water levels and temperature, the toxin was not correlated
with cyanobacterium biovolume since it was observed at high concentrations even long
after the cyanobacterium bloom had senesced. Sedimentation of microcystin in lakes,
and their relationship with biological and physicochemical variables was explored
by Song et al. [3]. Microcystin was detected in all sediment samples, and spatial
variability was observed among microcystins and cyanobacterial biomass in different
water levels and in sediments, highlighting the importance of the interaction between
water and sediments in the distribution of microcystins in aquatic systems.
HABs have an adverse impact in recreational waters by fouling beaches and shoreline,
affecting the quality of the water, and limiting recreational activities such as fishing,
swimming, and boating. The adverse effect of the occurrence of both marine and freshwater
toxic algal blooms in recreational waters in Washington State was discussed by Trainer
and Hardy [4], with a focus on monitoring efforts and the role of these efforts in
the protection of public health. In addition to regular monitoring practices for cyanotoxins,
the authors described the effectiveness of partnering state regulatory programs with
citizen and user-fee sponsored monitoring efforts in the surveillance and reporting
of HABs and how the combination of technologies provides a comprehensive system for
the protection of public health from exposure to HABs in fresh and marine waters.
Trainer and Hardy also discussed the role of forecasting systems for marine and freshwater
HABs, the basis for Wynne and Stumpf’s paper [5]. Wynne and Stumpf discussed in their
paper the usefulness of satellite data to examine spatial patterns of blooms and help
local communities and managers in planning. Satellites may help managers identify
patterns of bloom development and the areas most commonly impacted, some of them being
public water supplies or recreational areas. Spatial and temporal distribution of
blooms is also the topic of the paper by Van de Merwe and Price [6], though here the
emphasis is on the use of data from unmanned aircraft systems, then to correlate it
with cyanobacterial biomass densities at the water surface. The authors demonstrate
how these methods can provide valuable information that could help improve risk assessments
and risk management derived from traditional risk assessment methods.
HABs also could be present in drinking water and could potentially affect drinking
water treatment. Taste-and-odor problems have led some utilities to change processes
during the drinking-water treatment to decrease tastes and odors in finished drinking
water caused by algal blooms in the supply reservoir. Another problem is the presence
of cyanobacterial cells and toxins in finished drinking water. In the paper by Szlag
et al. [7], the authors concluded that conventional treatment effectively removed
cyanobacterial cells and toxins. The authors conducted monitoring of three toxins
(microcystins, anatoxin-a, and cylindrospermopsin), and toxin-producing cyanobacteria
on raw and finished water samples from five conventional drinking water treatment
plants experiencing cyanobacterial blooms in their raw water. One of the toxins, anatoxin-a,
was not detected in any of the utilities, and all finished water samples showed toxins
levels below the analytical methods detection limits.
Human health risks from exposure to HABs is another topic discussed in this special
issue. The paper by Hilborn and Beasley [8] used harmful cyanobacteria-associated
animal illnesses and deaths as sentinel events to warn of potential human health risks.
The paper primarily focuses on the One Health concept to integrate and collaborate
among disciplines as a way to effectively monitor environmental and animal health
as a way to assess human health risks. The authors concluded that illnesses or deaths
among livestock, dogs, and fish are all potentially useful as predictors for the presence
of cyanobacteria-associated human health risks. Human health risks surveillance is
also the topic of the paper by Backer et al. [9], with a focus on the reports from
States describing bloom events and associated adverse human and animal health events
collected in the Harmful Algal Bloom-related Illness Surveillance System (HABISS)
from 2007 to 2010. States used monitoring data to develop a wide range of public health
prevention and response activities including issuing public health advisories or beach
closures, and the development of public outreach activities. This work is indicative
of the need of attention to public health risks associated with human and animal exposures
to cyanobacteria and algae blooms. As mentioned before, HABs can cause adverse health
effects in both humans and animals as recorded in Kansas by Trevino-Garrison et al.
[10]. In this paper, the authors described the human and animal HAB-associated health
events in 2011, including reports of dog illnesses and several deaths, and human illnesses,
some of them requiring hospitalization. As part of its surveillance activities, the
Kansas Department of Health and Environment, in conjunction with their local and national
partners, developed a Harmful Algal Bloom Policy and Response Plan. This plan included
the investigation of reports of HAB-related cases, the evaluation of water sample
data, and education to the public of the public health risks. The authors highlighted
the importance of the development of policies and guidelines to prevent morbidity
and mortality among humans and animals.
Numerous techniques already exist for managing blooms in reservoirs. However, the
effectiveness of these techniques is relative. For example, Bauza et al. [11] exposed
water samples from a recreational lake with cyanobacteria to different concentrations
of hydrogen peroxide. Densities of cyanobacterial cells collapsed after exposure to
the highest concentration over a 48 hour period in the presence of light. The authors
concluded that the use of hydrogen peroxide could be used in hypertrophic systems.
As in Bauza et al. [11], the paper by Lürling et al. [12] also evaluates the effectiveness
of hydrogen peroxide to reduce cyanobacterial cells and their toxins in freshwater
systems, albeit this time also evaluating the effectiveness of ultrasound. Peroxide
effectively reduced toxin-producing cyanobacteria biomass at similar levels to those
found by Bauza et al., and proved to be ineffective at low levels. However, although
a reduction of toxins was observed, still a significant release of the toxins into
the water was detected. Ultrasound treatment only caused minimal growth inhibition
and some release of toxins into the water, showing the treatment to be ineffective
at controlling cyanobacteria. In these proposals, toxin reducing bacterial strains
are used in water reservoirs as another option that may help in the reduction of microcystins
occurrence. The use of bioreactors to eliminate microcystins is suggested by Dziga
et al. [13] as an alternative to chemical methods of cyanotoxins elimination. This
paper describes the effectiveness of using genetically engineered bacteria to degrade
microcystins, based on further research on the optimization of the technique and to
follow-up the long-term stability of the designed systems in natural conditions.
This special issue also includes a paper describing the development of guideline values
for cyanotoxins in the state of Oregon. In the United States, drinking water contaminants
are regulated under the Safe Drinking Water Act (SDWA). Currently, there are no regulations
for cyanotoxins in drinking water under the SDWA, but EPA developed in June 2015,
Health Advisories (HAs) for the cyanotoxins microcystins and cylindrospermopsin, to
assist federal, state and local officials in protecting public health from exposure
to these two toxins in drinking water systems. Regulations or guidelines have not
been developed either for aquatic life, aesthetics, or recreation in any body of water
under the Clean Water Act (CWA). In the absence of these guidelines, many US States,
including Oregon (Ferrer et al. [14]) have developed guidelines for cyanotoxins. The
Oregon Health Authority (OHA) developed guideline values for drinking water, human
recreational exposure, and dog recreational exposures for the four most common cyanotoxins
in Oregon’s fresh waters. This study shows that having cyanotoxin guidelines can give
rise to the development of toxin-based monitoring programs, which reduce the number
of health advisories, an important step in the protection of public health.
Public health professionals have taken measures to protect public health by assessing
and monitoring HABs occurrence and health effects, developing guidelines and HAB-related
public health programs, and implementing remediation and treatment technologies. Despite
these efforts, it is reasonable to say that the factors that promote HABs and their
toxin production, the health impacts, and the fate of these blooms and their toxins
in the environment is not totally understood. The different studies published in this
special issue recognized these knowledge gaps including the spatial variability among
cyanobacteria and their toxins in water and sediments, the complexity of monitoring
and inconsistency in treatment techniques, and the importance of the development of
guidelines for the protection of public health.