StevenR.Hilts,1 SusanE. Bock,1 TerryL.Oke,7 CherylL. Yates, and RaymondA. Cope9
'TrailLead Program Office, Trail, British Columbia, Canada;2Departmentof Health Care andEpidemiology, University of British Columbia, Vancouver, BritishColumbia, Canada
Trail,Canada,has been thesiteofanactivelead/zincsmelterfornearlyacentury. Since 1991, theTrail Community Lead TaskForce hascarriedoutblood leadscreening,casemanagement, educationprogrmstargetedat earlychildhood groups and the generalcommunity,community dustabatement,e4osurepathways studies, and remedial trials. From1989though1996,
aver-ageblood leadlevelsof children tested for the first time dedined at an average rate of 0.6 pgdl/year,while blood leadlevesinCanadianchildrennotlivingnear pointsouresappearedto belevelingofffollowingthephase-out ofleadedgasoline.Sincetherewas no concurrent
improve-ment inlocalenvironmenl cO tionsduring stime,itispossiblethat thecontinuingdecline inTrailbloodlead levels hasbeenat leastpartly duetocommunity-wide interventionprograms. Oneyearfollow-upofchildrenwhose families received in-homeeducational visits,aswellas assistancewith home-based dust control measures,found that thesespecificinterventions
pro-duced average blood leadchanges of+0.5--4.0plgdl,withstatisticailysignificant dedinesin3
yearsoutof5.Educationand dust control,particulalyactionstargetedtowardhigherrisk chil-dren,appea tohave servedaseffectiveand appropriate interim remedialmeasureswhile major
sourcecontrolmeasureshave been implemented at thesmeltersite.Keywork:bloodlead,dust control, environmental leadexposure, healtheducation, intervention, smelter contamination.
EnvironHealhPerspect 106:79-83 (1998).[Online21January1998]
h"t:llekpnel.
niehs.nib.gov/docs/1998/106p79-83hibrIabstr~html During the past two decades, numerousstudies havefoundneurobehavioural effects inchildreninassociationwithchronic low-levelleadexposure (1,2). In 1991, the U.S. Centersfor DiseaseControl releaseda state-ment establishing 15 pg/dl as the level at which individual children should receive nutritional and educational interventions andmorefrequentscreening(3). Canadian guidelines nowalso suggest 15 pg/dlas an individual interventionlevel (4).
Trail, British Columbia, has been the site ofalarge active lead and zinc smelter for nearlyacentury. Astudy conductedin Trailin1975 foundaveragebloodlead lev-els of22 pg/dl in 1-3 year olds (5,6). A more detailed study in 1989 founda geo-metricmeanof13.1 pg/dlin24-72month olds, with 39.4% of the samples above 15 pg/dl (7). Recommendations ofthestudy included theimplementation of a compre-hensive lead awareness and education cam-paignandprovidedtheimpetusfor creating theTrail Community Lead Task Force.
By autumnof1991,the Task Forcehad establishedacomprehensive childhood lead exposure prevention program.The program currently indudesannualblood lead screen-ingof children aged 6-60 months, case management, education programs targeted at early childhoodgroups and the general community, community dustabatement programs, exposure pathwaysstudies, and intervention trials. We have previously reportedonourworkinvolvingindoor dust control trials, ongoing soil treatment
experiments, and trends in community blood lead levels from 1991 through 1994 (8,9). This paper examines in more detail the effect thatcommunity education, dust control, and case management efforts appear to have had on children's blood lead levels in Trailfrom 1991 through 1996. It is not possible to precisely quantify the impact of these interventions, as the mea-sures were notwithheldfrommatched con-trol groups. Also, there isinsufficientdata to reliably establish the rate of decline in blood lead levels that was occurring in Trail prior tocommencementof the inter-ventionprograms.
Methods
Bloodleadscreening. Bloodsample collec-tionand analysis techniques, aswell as the age rangeofchildrentested,varied between earlierstudies and the current program. In 1975, blood samples were collected from children 12-36 monthsofage bythe fin-gerstick methodand analyzed by anodic strippingvoltametry. In 1989, fingerstick samples from children24-72months of age wereanalyzed byagraphite furnaceatomic absorption spectrometer with Zeeman backgroundcorrection (1J). In 1990, there was nogeneral blood leadsurvey;only chil-dren who had bloodlead levels of15 pg/dl orhigherin 1989 weretested as a
follow-up.
From 1991 through 1996, blood lead screening of children aged 6-60 months, who livedinthehighexposureareas 2 and
3 as shown in Figure 1, was carried out annually. Each year approximately 340 eli-gible children have been identifiedthrough health unit immunization records, birth notices, British Colmbia Medical Services Plan data, local day care centers, and kindergarten lists. The participation rate for theblood testing clinics has ranged from74 to 88%,with thehigher participation rates occurringinlater years. Familiesvoluntarily attendthe clinics at the Trail Lead Program office, where venous blood samples are drawn byan experienced pediatric phle-botomist after obtaining informed parental consent. Capillary samples are collected onlyinvery rareinstanceswhen venipunc-ture fails oris notacceptable to the parent orchild. Blood samples are collectedduring September each year, immediately after maximum summer exposureconditions are known toprevail.
Blood samples are analyzed using a graphite furnace atomicabsorption spec-trometerwith Zeeman background correc-tion (10). The following quality control (QC) procedures are used to verify the accuracy and precision of the blood lead measurements: random splitsamples from children areanalyzed at both thestudy lab-oratory andaQClaboratory; replicate sam-ples from adult volunteersare submitted weekly to the twolabs; certified reference blood from the National Institute of Standards andTechnology (NIST) is sub-mittedweekly to thetwolabs; blood collec-tion tubes andsupplies are prescreened for contamination prior to theclinic; and all blood sample tracking data is double entered into acomputerized database man-agementsystem and cross-checked for accu-racy. The annual blood lead clinics cost approximately $65,000 (Canadian).
AddresscorrespondencetoS.RHilts,Environmental
Coordinator, Trail LeadProgram Office, 843 RosslandAvenue, Suite 300,Trail,BritishColumbia,
ViR4S8 Canada.
This workwasfundedthroughgrants tothe Trail
CommunityLead Task Forcebythe British Columbia
MinistryofHealth,the British ColumbiaMinistryof
Environment, Lands andParks; Cominco, Limited;
and theCityof Trail. TheRotary ClubofTrail,with
funding from the Task Force and from the
Environmental CitizenshipInitiative(Environment Canada), organizedandimplementedmuch of the communitydust abatementworkdescribedherein.
TheauthorsaregratefultoNelsonAmesfor his com-ments on anearlier version of thismanuscript. Received27May 1997;accepted20October 1997.
Figure1.Trail residentialareas.
Case management. Blood lead results of 15 pg/dl or higher for children 20 monthsof age and older, or greater than 10 pg/dl for children under20 months of age triggerthefamily'sinclusionin a case man-agement program. The casemanagement programbeganin 1991 andcurrently con-sists ofmore frequent blood lead testing; in-homecounseling onexposure reduction measures such as dust control, hygiene,
nutrition, and yard care; lead testing of bareground, house dust, painted surfaces,
etc., to highlightareas needing immediate attention; provisionofentrancemats, sand-boxes with clean sand and lids, ground cover materials, and house cleaning sup-plies orservices; and assistancewith paint abatement. Cleaning supplies may include mops, buckets, detergent, and loaned or
purchasedvacuum cleaners. Cleaning ser-vices include regular vacuuming, wet wip-ing, and mopping (9). Approximately
$70,000 (Canadian) per year is spent on thecasemanagement programs.
Education. Exposurereduction mes-sagesaredelivereddirectlytoyoung children through semiannual visits to play schools, daycare centers, and kindergarten classes. Puppets, a model house, and a unique demonstration of the needfor careful hand washingare used toteach young children about hygiene, nutrition, and safe placesto play. Materials and financial contributions are also provided tothese groups to assist with deaning andyardmaintenanceandto facilitate handwashingattheir facilities.
Duringthe annual fall blood screening clinics, families are offered hand soap, a doormat, and various written educational materials toreinforce the messages ofgood hygiene, good nutrition, and minimizing house dust. They are also providedwith lead exposure reduction guidance tailored to such factorsasage of their children and theirareaof residence. The LeadProgram's public health nurse also meets with local physicians, makes presentations atprenatal classes,visitsmothersinthehospital mater-nity ward, andvisits families in their homes. Trailareacommunityhealthnurses also indude lead educationaspartof their regular well-babyvisits.
The Lead Program's exposure reduction messages, as well as news about program activities and progress, are communicated to the generalpublic through distribution ofanewsletter three times per year to all residentialmailing addressesinTrail, adver-tisements in local print and radio media,
billboards, public displays, andquarterly Table 1.Summaryof educational contactsbythe TrailLeadProgram1September1991-31August1992
No. ofpresentations No. of contacts No. of contacts No. of minutes in Type ofcontact Particularsofcontact orissues withchildren with adults contactper group orfamily
Contacts with School bulletin boards 8 9,600 480
educational groups Artwork/circle time ideas 10 4,080 268
Meetingswithorpresentationstoelementary 55 525 55 25
schooladministrators,teachers, and students
Meetingswithorpresentationstodaycare 18 240 45 45
directors, instructors,and students
MeetingswithorpresentationstoMom&Meleaders, 9 290 137 35
mothers,andchildren
Subtotals 100 14,735 985
Healthpromotionand Screeningclinicanticipatory guidance 300 100 400 10
casemanagement Phone/letterfamilycontacts 880 0 1,075 4
contacts Home/office counseling visits 275 150 350 40
PHNcontactswithfamilies 240 30 300 10
Meetingswithhealthprofessionals 10 0 48 30
Prenatal classes 11 0 154 30
Subtotals 1,716 280 2,327
Generalcommunity General community newsletter 1 0 7,050
contacts School newsletters to parents 10 0 16,800
Localnewspaper educational ads 6 0 81,840
Publicmeetings 12 0 10 60
Miscellaneous functions(infobooth,etc.) 5 50 360 3
Subtotals 34 4,100 106,060
Grand totals 1,850 19,115 109,372
newsletters sent to parents through schools, play schools, and day care centers.
Table 1 provides a summary of the wide varietyof contact types, groups reached, and number ofcontacts made in 1991-1992, which was the first year ofoperation of edu-cation and case management programs. Approximately$70,000 (Canadian) per year isspent oneducation programs.
Community dustabatement. Since
1992, the following dust control measures have been carried out in the Trail area: annual spraying of dustsuppressant on unpaved alleys and parkingsurfaces; green-ing of bare public areas usgreen-ing turf or seed; covering of bare areas using asphalt, con-crete, or gravel; andmore frequent sweep-ing and washing of paved streets. The Rotary Club of Trail and other public groups have been instrumental in organiz-ing and carrying out much ofthis work. An average of$17,500 (Canadian) has been spent each year since 1992, not including thecostofstreetcleaning.
Environmental monitoring. Soildata were obtained from studies conducted in 1977 (6), 1989 (7),and 1992(11).Ineach ofthestudies, sampleswere collected from the top 2-3 cm of the soil profile and
digested innitric/perchloric acids prior to
analysisfor lead. In1977, thesampleswere not sieved, whereas in 1989 and 1992,
samples were passed through a 180-pm screen before analysis. This report consid-ers samples collected from the same geo-graphic areasineachof the 3study years.
Data for leadin suspended particulate,
leadin dustfall, and number ofdayswith rainwerecollected by the smelter company. Suspended particulatewascollected for24hr every6daysbytwohighvolume airsamplers
locatedinthe immediate Trailarea. Dustfall was collected monthlyinplasticjarslocated atnine sites in the immediate Trail area;
however, analysisof dust fallsamplesfor lead did not start until 1991. The sampling
equipment, samplingsites, analytical tech-niques, and qualitycontrol procedures for suspended particulate and dust fall datameet BritishColumbia Ministry ofEnvironment (BCMoE) requirements. A qualitycontrol sampling station isoperatedin Trail bythe BCMoE to verify results obtained by the smelter company. Datafrom the audit sta-tionwere notusedinthis
analysis,
asthe sta-tiondidnotoperateduring partof1995 and 1996 due toconstruction activities nearthe site.Precipitationwasrecordedatthe smelter siteas part oftherequirements ofaweather observation program operated by theAtmospheric Environment Service
(EnvironmentCanada).
Dataanalysis.Analyses were conduct-edtoexaminetheeffects of boththe
general
community-wide intervention efforts and themorespecific one-on-one case manage-ment efforts. To distinguish between these effects, we conducted separate analyses of blood lead datafor children tested for the firsttime ineach year and forchildren who received repeat testing subsequent to in-home case management intervention. The former analysis excluded children with oldersiblings who had been tested
previous-ly, and thelatter analysis excluded those whose families had already received case managementinterventionforoldersiblings.
Frequencyplots of blood and environ-mental lead data indicated that the data werelog-normally distributed.Averages are expressedasgeometric means, and hypoth-esis testing and regression analyses were performedonnaturallog-transformed data. Age and area adjustment of log-trans-formed blood lead datawas performed using analysis of covariance (12) to com-pensate foryear-to-year differences in the age and area ofresidence distributions of participantswherenecessary.
Results
Figure 2shows the trendingeometricmean blood lead levels for children testedforthe first time in eachyear from 1989 through 1996 (therewas no blood lead surveyin 1990). The age and area distributions of childrentestedvariedsignificandy(p<0.01) fromyear to year, so ageandarea-adjusted blood leadaverages arepresented. In multi-ple regression analysis with blood lead as the dependentvariable, the year of testing enteredinto theregression modelevenafter adjustment forage andarea (see Table2). The regressionshowedadeclining trend of 0.6 pg/dl(orabout5%) per year.
Changes in local environmental lead levels andweatherconditions were investi-gated to determine whether the 0.6
pg/dl/year decline in average blood lead levels in Trail might be due to improve-ments in local conditions. Table 3 shows theaverage soil lead levels in Trail from 1977 to 1992. The differences between years were not statisticallysignificant, even when paired analysis bypostal codes was conducted on the 1975 and 1989 data (13). Therefore, the decline in blood lead levelsfrom 1989 to 1996 is notduetoany improvementin soil lead levels.
In infants and toddlers, where skeletal lead contributes arelatively small portion of total blood lead concentration, lead in blood is generally thought to reflect fairly recent exposure (i.e., the past 30 days) (14). Manyof the children testedannually
in Trail,particularly those aged 3-5 years, have been chronically exposed to lead for severalyears, and theirpresentblood lead
levels are much more
dependent
uponlonger
term past exposures. However, theyear-to-year
variability
in average bloodlead levels in Trail
might
beexpected to correlate with exposure conditionsduring
the summer months prior toeach annual blood testingclinic. Wetherefore choseto look atenvironmental and weather condi-tions
during
the summers preceding each ofthe annualblood lead clinics.Possible
relationships
betweenbloodlead andairlead,
dustfaUlllead,
andthe number ofdays
withoutrainfallintheJunetoAugustperiod
wereexamined. Inmultiple
regres-sion, nostatistically significant correlations werefoundbetweenaverageblood lead level andair
lead,
dustfalllead,ornumber ofdry
days
foreither the whole summerperiod
orforanysubset ofit.Table 4shows that there
clearly
hasnotbeenanytrendinAugust val-ues forambientairlead,
dust falllead, or number ofdry days
over the 1989-1996period. Therefore,
thedecline in blood lead levels from 1989to 1996 doesnotappearto bedue to changes in summerairlead, dust falllead,orweatherconditions.Table5 presentsresults forchildren who hadelevated blood lead levels (.15
pg/dl)
CD 16 |_
1
- 149 19 1 3 1 1 lO
Fiur 2. Age an araajse geometric mean
Z 0 _ _2-ll1iS _
blood lead levels of children tested for the first
time, byyear. The regression line represents
1989-1996means.
Table 2 Regressionmodel for effect of yearonblood
lead
Independent Regression Standardized
variable coefficient coefficient p-Value
Age 0.0670 2.52 <0.0001
Age2 0.00212 -5.07 <0.0001
Age3 0.000195 2.65 <0.0001
Area 0.203 0.240 <0.0001
Year -0.053 -0.271 <0.0001
Thedependentvariable isln(bloodlead);themultiple correlationcoefficient=0.39.
Table 3.Geometric mean soil lead concentration in
Trail, Britsh Columbia
Number Soil lead
Year ofsamples (ppm) Reference
1977 153 7908 (6)
1989 119 725 (7)
1992 213 713 (11)
&Sampleswere notsievedprior to analysis and may be biased low incomparisonto1989 and 1992 data.
Table 4.Blood leadscreeningresults and concurrent environmental conditions
Parameter 1989 1991 1992 1993 1994 1995 1996
Blood lead(pg/dl)8
No.of children 169 197 118 99 95 76 46
Ageandarea-adjusted geometricmeanb 14.5 13.4 11.9 11.3 12.1 9.5 11.0
Leadinsuspendedparticulate(pg//m3)
Geometric mean(August) 0.98 1.1 2.7 0.51 1.5 0.71 1.8
Lead indust fall(mg/m2/day)
Geometric mean(August) NA 2.6 1.7 1.4 1.4 0.81 2.4
Weather
No.ofdayswithout rain inAugust 13 22 25 19 27 19 24
NA, notavailable.
aSeptemberclinic;children in areas 2 and 3 whoweretestedfor thefirsttime.
bBloodleadmeanshave been age- andarea-adjustedtoallowcomparison by year.
Table5.Children's blood lead levelsfollowingcasemanagementintervention
Average Averagechangein
Yearchildren Number of age Averageinitial blood lead in group Paired received children atenrollment blood leada 1yearlater t-testp-value
intervention in group (months) (pg/dl) (pg/dl) forchange
Childrenreceivinginterventionb
1991 77 39 19.8 -4.0 <0.0001
1992 34 33 18.4 -3.1 <0.0001
1993 14 21 20.4 -2.3 0.10
1994 25 27 18.2 -3.1 0.0001
1995 14 30 17.4 +0.5 0.71
Childrenwho didnotreceive intervention
1989 55 48 19.8 +1.2 0.16
&All data in thistableareforchildren who hadanelevatedbloodlead level(.15 pg/dl)priortointervention.
bDatain thissectionarefor children whosefamiliesreceivedcasemanagementintervention for the first time.
and whoweretested again1yearafter their families received targeted interventions
under the case management program
described above. Ineach year, greater than 90% ofeligible families accepted in-home counseling andassistance with exposure reduction measures; thus, the number of children with elevated blood lead levels who did not receive interventions ineach yearisverysmall.Therefore,theonly avail-able comparison iswith the children who had elevated blood lead levels in 1989, as interventions were not provided in that year. Those children showed an average increase of1.2 pg/dl when tested 1 year later. The difference was not statistically
significant. In contrast, when the blood lead levels of counseled childrenhavebeen rechecked 1yearlater, the average has usu-ally declined by statisticusu-ally significant amounts (2.3-4.0 pg/dl). The notable exception was from 1995 to 1996, when the blood lead levels of the small number ofchildren who received interventions for the firsttime did not change significantly. There was no significant relationship betweenage and changeinbloodlead level among the children involved. Therefore, despite the declining average age of
chil-drenenrolled in case management forthe firsttime, therewas no need to age-adjust theblood lead data.
Discussion
There does not appear to have beenany increase intherateofdeclineinblood lead levels of Trail childrenfollowing the intro-duction ofinterventions in late 1991. As mentioned above, thereis insufficient data to reliably establish therate of decline in blood lead levels that was occurring in Trail priorto 1991. However,theconstant andgradualdeclineseen in blood lead lev-els of Trail children from 1989 through 1996roughly parallelsageneral worldwide drop inblood lead levels seen during the period from about 1976 through 1994
(15-15)).
Infact, the global rateofdecline has been about 0.8-1.5 pg/dl/year, rather than the0.6 pgldl/yearseen in Trail. The global declineisthought to be duetosuch actionsasthephase outof leadingasolineandpaint,the discontinued use of lead sol-der infoodtins, and reductionsinair emis-sions from industrial plants. In Canada, where leaded gasolinewas eliminated by 1990, the Ontario Blood Lead Study found thataveragebloodlead levels in
chil-drennotlivingnearpointsourcesdeclined byabout1.3 pg/dl/yearfrom 1984to1990 and then appeared to level off (20). Therefore, it appears that the decline in blood lead levels in Trail from 1991 through 1996mustbe at leastpartlydue to local changes. As presented above, there
was no corresponding improvement in localenvironmental conditions during this period. Therefore, it is possible that the continuing decline in Trail children's blood leadlevels may beatleastpartly due to the implementation of(and annual improvements in) community-wide inter-ventionprograms.
In the 1-yearfollow-up of Trail chil-dren whosefamiliesreceived in-home edu-cational visits, as well as assistance with exposure reduction measures, we found that these specific interventions produced average blood lead changes of +0.5- -4.0
Ig/dl, withstatistically significant declines in3years outof 5.Anumberofother pub-lished studies have also examined the effectsof educational efforts and/or assis-tancewithmeasuressuchashousecleaning or groundcover improvement.Astudyof in-home education efforts in Milwaukee, Wisconsin, involved 431 children up to 6 years of age with initialblood lead levels of 20-24
pg/dl
(21). Advice on nutrition, behavior change, and housekeepingwas providedto families of 195 childreninthis group.The remaining 236 children did not receivevisits,either becausethey were iden-tified before the educationvisits werebeing offered or because their families could not be contacted. Themean decline inblood lead in the group receiving visits was 4tg/dl. The net difference in blood lead change between groups, after adjustment for age and seasonal differences, was 3 pg/dl (p= 0.001). Another group of28 Milwaukee children with initial blood lead levels of25-40 pg/dl received the same homevisit as in the previous study, plus a visit from a public health nurse (PHN) who conducted a child health assessment and answered any questions about lead (21). There was no control group in this study, as virtually all families eligible for this program were contacted. The mean decline inblood lead in this group was 6
pg/dl, which suggests that greater declines may beachieved when initial blood lead levelsare higher,orthat thesecond visit by the PHN may have provided additional benefit.
Astudyin the formersecondary lead smelter town ofGranite City, Illinois, involved 78 children under 6 years of age who had initial bloodlead levelsgreater than 9 pg/dl (22). Theparents of these children received in-home counseling visits lasting about 30-45 minutes. The visits included adviceon hand washing, nutrition, house-keeping, hand-to-mouth activity, and simple paintabatementwhere indicated.There was nocontrol group.At 1 yearfollow-up, the average blood leadlevel had declined by 5 pg/dl, which is a particularly noteworthy
decreaseconsidering thatthe averageinitial bloodlead levelwasonly 14.6
pg/dl.
Acontrolled trial ofregularwet mop-ping offloors,combined with advice regard-ing handwashing, housekeeping, and lead "hot spot"avoidance, found that the average blood lead level of the group receiving inter-ventionfell from 38.6 pg/dlto31.7jig/dl(a drop of 6.9 igIdl), while that of the control groupfell by only 0.7lig/dl(23).
Amore recent study found that a com-bination of interior painted surface cleanup,house cleanup with a HEPA(high efficiencyparticulate air) vacuum, mopping withhigh phosphate detergent, some car-petremoval, coveringof bare soil with sod orbark, provision of clean sandboxes, pro-vision ofhousehold cleaningsupplies, and provision of dust controlinformation was effective in preventing aseasonal rise in blood lead levels(24).
Acontrolled trial of regularHEPA vac-uuming of interior floorsinTrailfailed to show aclinically significant impact on either blood lead or floor lead levels (8). However, anuncontrolledfollow-up study suggested that a combination ofregular HEPAvacuuming, wet mopping, exposure reduction advice, and assistance with ground cover improvement was successful in reducing the summer seasonal rise in blood lead levelsandinpreventing the sea-sonalrise infloor lead loadings (9).
Overall, this report suggests that
com-prehensive, community-wide interventions such aseducation, greening, and other dust controlmeasures mayhave had an impact onbloodlead levelsin Trail. However, the lack of a control grouporadequate baseline data make itimpossible to conclude that theseactionshave hadameasurable impact. Onthe otherhand,interventions specifical-ly targeted toward children with elevated blood lead levels do appear to have an impact. Targeted interventions such as in-homecounseling and assistance with home-based exposure reduction measures have
been associatedwith reductions in blood leadlevels inTrail, aswellas atother sites. These targeted interventions have servedas
effectiveand appropriate interim measures in Trail while the smelter company has been implementing critical source control actions, such as the reduction offugitive emissions and the construction ofanew state-of-the-art lead smelter. It is recom-mendedthat in-homecounseling and assis-tancewith home-based exposure reduction activities be implemented and studied as preventive measuresfor infants, rather than
focusing onlyonchildren whoseblood lead levels are alreadyelevated.
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