Risk Assessment of
- Collation and review of published and unpublished data on
- Simple assessment of the risk of BMAA to human health
through drinking water.
- Identification of gaps in information.
The finding of the non-protein amino acid,
β-methylamino-l-alanine (BMAA) with neurotoxic properties in
the brain of patients with degenerative disorders and its reported
presence in cyanobacteria found commonly in water sources used to
provide drinking water has led to concern over its potential widespread
effects on human health. This report collates the information currently
available to inform a risk assessment of BMAA through this route.
- No risk assessment can be made because of the extremely
limited current state of knowledge on BMAA.
- Toxicological studies indicate that BMAA is a neurotoxin
although some experiments indicate that it has only a weak effect on
systems concerned with the neurotransmitter, glutamate. There is also
some evidence that it may not easily cross the blood brain barrier.
There is a lack of toxicological information based on standard tests
using the oral route of exposure which is more relevant to
environmental exposure upon which to base a health-based value for use
in a risk assessment.
- At present, there are insufficient data to confirm an
association between the presence of BMAA in the brain and degenerative
diseases and this remains a hypothesis.
- BMAA appears to be present in laboratory cultures of a wide
variety of cyanobacteria from natural blooms. However, there have been
some contradictory results and more data are required to confirm that
BMAA might be present in natural waters.
- Intact cyanobacteria have been shown to be removed by the
mechanical processes of drinking water treatment; however, lysis of
cells may release cyanotoxins including BMAA. This may be less for BMAA
than for other toxins because at least a portion of BMAA may be
protein-bound and potentially less likely to be released from the cell.
- While drinking water treatment methods such as
chlorination, ozonation and granular activated carbon (GAC) may remove
other cyanotoxins, the simpler structure of BMAA may make it less
susceptible to these types of treatment, particularly breakdown by
oxidants. However, there is no evidence for this at present.
The following knowledge gaps have been identified, where further
research is required before a meaningful assessment can be made of the
potential risk posed by BMAA to human health, particularly by exposure
via drinking water:
- Further studies on the toxicity of BMAA are required
including the use of standard protocols using the oral (and to a lesser
extent dermal) route of administration which is more relevant to
- Measurement of the physicochemical properties of BMAA would
give information on its fate and behaviour in the environment;
- Agreement on the standard analytical protocols to be used
for the measurement of BMAA in cyanobacteria, water, foodstuffs and
- More confirmatory information is required on the presence
of BMAA in cyanobacteria;
- Laboratory studies on the removal of BMAA by drinking water
- Monitoring of raw water sources in the presence of
cyanobacterial blooms; and
- When the toxicity assessment is adequate to set a Tolerable
Daily Intake, monitoring of drinking water should be undertaken.
Copies of this report may be available as an Acrobat pdf download under the 'Post 2000 Reports' heading on the DWI website.