I I

INVESTIGATING HEALTH RISKS FROM RIVERINE BLOOMSOF BLUE GREEN ALGAE

I ii November 1991 the world's largest recorded riverinebloom of blue green algae occurred along 1000km of the

Darling-Barwon river system (Figure 1). A state ofemergency was declared to coordinate the provision of safedomestic water supries for towns, Aboriginal communitiesand landholders.

DARLING-BAR WON ALGAL BLOOMSNOVEMBER-DECEMBER 191, NSW

r'•Estrerne lstornge, weir(river) .

O- Low/Moderete ntorage. weir/river)Occurrence of blue-green nigel bkioms(áoe not inrk,de farm damsi

After potable water supplies had been secured for thesecommunities, there were three outstanding public healthissues:

• how many individuals did not have access to anuncontaminated drinking water supply;

• does filtration eliminate the cyanobacterial toxinsfrom potable water, and if not what health risks areassociated with drinking filtered water; and

• what are the health risks of recreational exposureto water contaminated with algal blooms.

The NSW Blue Green Algae Task Force Final Reportidentified a nui-nber of environmental conditions whichfavour the development of these blooms - high nutrientlevels, nitrogen:phosphate ratios less than 29, watertemperature above 20°C, high pH, abundant zooplankton,low water flows and reduced water turbidity. The task forceconcluded that:

'The Australian environment is characterised by many ofthese environmental conditions - - - (There is) an existingand increasing potential for algal problems throughoutmost of western NSW and in many coastal rivers."

The likelihood of further outbreaks in the Darling-Barwonriver system and elsewhere in NSW underscores the needfor better information about the likely health effects ofexposure to blue green algae.

In late October 1992 algal blooms had reappeared in theriver between Louth and Culpaulin. The most commonspecies found was Anabaena. This paper presents anassessment of options for future surveillance of illnessrelated to algal blooms and the feasibility of more detailedepidemiological investigations of this problem.

BACKGROUNDBlue green algae (or cyanobacteria) are primitivephotosynthetic organisms which are widely distributedin inland waterways. Two genera of these cyanobacteriadominate the records of nuisance blooms in NSW:Amsbaena and Micro-cystis'. Deaths in livestock drinkingcontaminated water can be attributed to the neurotoxinsand hepatotoxins produced by these algal species. Reportsof adverse human health effects are inconsistent. Mostcommonly reported are eye, skin, gastrointestinal andrespiratory symptoms following immersion in heavilycontaminated blue green algal scum2. Concerns have beenraised about the possible long-term health effects of lowlevels of this toxin in potable water .

In collaboration with the South Australian HealthCommission and the National Centre for Epidemiology andPopulation Health, a case definition for blue green algae-related illness was proposed (Table 2).

CASE DEFINITION OF BLUE GREEN ALGAL-RELATE F) ILLNESS

One or more of the foPlowing symptoms

• conjunctivitis withoutdischarge

• blisters on the lips orin the mouthmyalgia with fever

• allergic respiratorysymptoms: hayf ever andasth ma

• skln rash with/withoutitch

• gastroenteritis: nauseaand/or diarrhoea and/orvomiting and/or

Previous reports suggest that illness associated with bluegreen algae is most likely to occur within 24 hours for skinexposure and within 48 hours for consumption.

The design of meaningful epidemiological studies of illnessrelated to this cyanobacterial bloom is severely constrainedby the small populations involved and the remoteness of theaffected communities. A case control study, using patientsattending general practitioners in these communities as asource of both cases and control subjects, was planned. Bythe time this development work was completed in February1992 the bloom had effectively receded.

INVESTIGATIONA preliminary visit was made to Wilcannia on November 2,accompanying the Royal Flying Doctor Service (RFDS) onone of its ti-i-weekly visits. It had the following aims:

• to conduct a pilot survey of people attending theRFDS clinic in Wilcanriia which could:

- identif' possible cases of cyanobacterial-relatedillness

- identify likely sources of exposure tocontaminated water (either for drinking, bathingor swimming)

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Blue green algae

Continued from page 27

- test the feasibility of conducting a case controlstudy based on attendances at a generalpractitioner or RFDS clinics;

to obtain qualitative information from RFDS,hospital and community health staff, schoolprincipals and school nurses in Wilcannia aboutpossible cases of cyanobacterial-related illnessoccurring in recent weeks in the community andabout likely routes of exposure to contaminatedwater and high-risk groups;to determine the best methods for surveillance ofdisease associated with blue green algae, includingrefinement of the case definition;to investigate avenues for future epidemiologicalstudies; andto enlist cooperation for any future investigationsfrom the staff of the RFDS, Wilcannia Hospitaland the local schools.

General practitioners in other communities affected by thealgal bloom were contacted to request information on anyrecent illness that might be associated with the algal bloomand to assess their willingness to participate in a casecontrol study.

OUTCOMEReports from the Department of Water Resources documentthe rise in the number of cyanobacterial organisms in theriver at Wilcannia, between October and December(Figure 2).

On October 17, two teenage girls with gastroenteritis andmyalgia were seen at Wilcannia Hospital. One requiredadmission. Symptoms had appeared after both girls hadswum in the Darling River. The symptoms resolved after48 hours. Health professionals reported no apparentincreases in the incidence of illness that might be associatedwith blue green algae. Some residents reported itchy skinrashes after showering, even after carbon filtration of thetown water supply began on October 26.

Of the 26 patients surveyed at the Wilcannia HospitalClinic on November 2, only one had symptoms that fitted

ANABAENA CELL COUNTS. DARUNG RIVER.WILCANNIA, SEPTEMBER-NOVEMBER. 1992

crlsIm1 Thov,th)

DATE OF SAMPLINGData: River Watch Program,Western Total Catchmcnt CommitteeNSW Department f Wner Resources

the case definition. The symptoms reported wereconjunctivitis and allergic respiratory symptoms. Thisperson reported no contact with any source of unfilteredwater affected by blue green algae.

Most participants reported drinking town water (77 percent) and/or rain water (30 per cent). Town water was usedmost frequently for bathing and showering. None of thesurvey respondents reported a history of swimming orparticipation in water sports in the previous 24 hours, andonly 20 per cent had other contact with unfiltered water.

School nurses and hospital staff reported that the mostlikely groups at risk of exposure were:

children over six years of age, especially those fromthe Aboriginal community, who swim in the river.The popularity of swimming in the river did notalter during algal blooms, and the closure of themunicipal swimming pool had probably maderecreational exposure to contaminated water morecommon;young adults who participate in water skiing alongthe river;those exposed to untreated town water used in thegarden such as gardeners, and children who rununder the sprinkler;all the townspeople who were exposed in the five-seven days between testing the river and thewarnings given by the Department of WaterResources and the local shire;people in properties along the river that pump waterdirectly from the river for consumption and bathing.

Many general practitioners in these remote communitiesexpressed a reluctance to participate iii a case control studybecause of time limitations and their perception that it wasnot a significant health problem.

CONCLUSIONThe results of a pilot survey ill Wilcannia would suggestthat despite evidence of numerous opportunities forsignificant recreational exposure to algal contaminatedwater there was very little evidence of health problemsoccurring as a direct result of that exposure. There were twocase reports of gastrointestinal illness in river swimmers.The only other reports of illness were some of minor skinirritation.

The information provided by this investigation may not givea complete picture of illness in the community and thereforecannot provide convincing evidence that blue green algaeposes no significant health problems. Therefore concernsabout the safety of water contaminated with blue greenalgae remain.

However, we concluded that a more detailed epidemiologicalstudy, such as a case control study of patients attendinggeneral practitioners, was not warranted or feasible at thistime in the isolated cormmmities along the Darling because:

• people living in remote areas may not seek medicaladvice for the minor ailments which exposure toblue green algae might cause; and

• some doctors and others in the cormrnmity along theDarling River do not perceive illness related to bluegreen algae to be a health priority.

VoI.4/No.3 28

Sept25 Oct 5 Oct15 Oct25 Oct2S Soc 2 5cc, 16 Nov23 Dec 7 Dec14

PUBLIC HEALTH ABSTRACTSBlue

Continued from page 28

The most promising avenue for future epidemiologicalresearch would be school-based studies. Children living alongthe Darling swim frequently in the river. School nurses are ina unique position to monitor even minor illness among thesechildren. The most appropriate option for future surveillanceof this potential public health problem would be to monitorcontinuously trends in blue green algae-related illnessesreported to school nurses in areas regularly affected byriverine blooms of blue green algae. Increases in the incidenceof blue green algae-associated illnesses during or followingalgal blooms would indicate the need for furtherepidemiological study.

Margaret Williamson, Stephen CorbettEpidemiology and Health Services Evaluation BranchNSW Health Department

ACKNOWLEDGMENTS

We greatly appreciated the help provided by Dr John Affleckand the staff of the Royal Australian Flying Doctor Service,Matron Joan Edgecombe and the staff of Wilcannia Hospitaland Community Health, the principals and staff of theWilcannia Central School and St Teresa Community Schooland the community at Wilcannia.

1. Blue Green Algae Final Report. Blue Green Algae Task Force, NSWDepartment of Water Resources, 1992.2, Hunter PR. Human Illness Associated with Freshwater Cyanobacteria(blue green algae). Public Health Laboratory Service Microbiology Digest1991; 8:3; 98400.3. Falconer 113, Beresford AM, Runnegar MTC. Evidence of liver damageby toxin from a bloom of blue green algae. Med JAust 1983; 1:511-514.4. Collins M. Algal Toxins. Microbiological Reviews 1978; 42141:725-746.

Mammo graphic screening

Continued from page 26

The satisfaction of women with the service provided at thetime of the first screen will be an important influence ontheir decision to have future screens. A survey of womenattending the screening and assessment services in theCentral and Hunter Area Health Services was begun inJune 1992. The results of the survey will be taken intoaccount in the planning of the new services to ensure thatservice provision meets the perceived needs of women.

Pi-inted materials about marnmographic screening havebeen written in consultation with consumer representatives,health providers and educators arid will be distributed bythe services.

Community education is a major issue in developing publicknowledge and acceptance of the manimographic screeningprogram and fostering recruitment of the target population.Strategies to involve health promotion personnel in thebroadest sense will be developed through a series ofseminars about breast cancer and mammographicscreening. The seminars will be developed on a consultativebasis by the State Planning and Co-ordination Unit.

Ellen Ryan, Manager, State Planning and Co-ordinationUnit for Mammographic Screening, NSW Cancer Council

T he following abstracts were prepared for the NSWPublic Health Network Conference in Sydney in

November. The presenting author's name is i.mderlined.

BEHAv10URALJRI5K FACrOR SURVEY IN A RURAL AREAThree communities in the South West Region weresurveyed using a telephonebased methodology. The almsof the survey were to pilot the use of telephone surveys ina rural area and to gather local behaviouraL'risk factor data.The survey employed random digit dialling and the randomselection of household participants, over the age of 18 years,using Kish Grids. Questions were taken (or modified) fromthe National Health Survey and National Heart FoundationRisk Factor Survey or were developed locally followinginput from a community meeting. The survey includedspecific questions on injuries related to farm work as wellas questions on the perceived major health problems in thecommunities surveyed.

Students from La Trobe University Albury/Wodongacampus were trained as interviewers. Interviews wereconducted between 630pm and 830pm Monday to Fridayfor a period of three weeks with 480 interviews beingcompleted. Despite intense and supportive local mediacoverage the response rate was 62 per cent. The cost percompleted interview (not including data entry and analysisand questionnaire development) was approximately $12.Analysis of the data is being undertaken. A major issuewhen conducting these surveys in rural areas is the lackof experienced interviewers.

Tony Kolbe, Kim Gilchrist, Elaine Clark and Neil Stubbs

THE SYDNEY AIR POLLUTION AND MORTALITY STUDYThere has been increasing community concern over visibleair pollution hi Sydney and its possible effect on health. Thispaper reports the results of an analysis of daily death countsand environmental variables in the Sydney area of NSW forthe period 1986 to 1989. The study determines the associationbetween daily air pollution (nitrogen dioxide, ozone andnephelometry, an indirect measure of particulates) andmortality.

All available air pollution data were obtained from the thenState Pollution Control Commission from 1986 to 1989 forall sites in the Sydney area. Meteorological and mortalitydata were collected for the same time period and area.Multiple linear regression models were fitted to the dataset,with non-traumatic deaths as the outcome variable. Varioustechniques were used to account for autocorrelation.Separate models were fitted for seasons and additionalanalyses were performed using the alternative outcomevariables of cardiovascular deaths and cancer deaths.

The base model found significant effects of temperature,nitrogen dioxide, day of week and seasons in predictingthe nm'nber of non-traumatic deaths. The reduced modelaccounted for 38 per cent of the variability in daily non-traumatic deaths. An increase of one log unit of nitrogendioxide is associated with an increase in daily deaths of two.An increase in nitrogen dioxide levels from 0.0 to 2.7 pphmwould be associated with an extra two deaths on that day.If nitrogen dioxide levels increased by a further log unit,from 2.7 to 7.4 pphm, there would be a further two deaths.

Peter Lewis, John Wiodarczyk, Stephen Corbett and TimChurches

1 Henry E. Bid to reduce breast cancer deaths. NSW Public HealthBulletin, May 1991. Volume 2, Number 5.

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