Regular House Cleaning Can Reduce Blood-Lead Levels in Young Children
The Robert Wood Johnson Medical School conducted a randomized, controlled trial to test whether an education and house-cleaning intervention can reduce blood-lead levels in young children who are at risk for lead poisoning.
The study took place from 1991 to 1997 in Jersey City, N.J., where 113 urban children between the ages of 6 and 36 months participated.
Fifty six children received a lead-dust intervention composed of education for their mothers and biweekly assistance with household cleaning, and 57 children were placed in the control group, which received training in accident prevention.
- Of these 113 children, 99 were successfully followed for 12 months (plus or minus 3 months): 46 in the lead-intervention group and 53 in the control group.
- During the study period, blood-lead levels fell 17 percent in the intervention group and did not change in the control group.
- Household dust and lead-dust measures also fell significantly in the intervention group. Children in homes that were cleaned 20 or more times over the year had an average blood-lead reduction of 34 percent.
- The study's results indicated that regular home cleaning, accompanied by maternal education, is a safe and effective intervention that may be useful for the large majority of lead-exposed children for whom removal to lead safe housing is not an option.
Fourteen articles have been completed and have appeared in publications such as Pediatrics, the Journal of Exposure Analysis and Environmental Epidemiology, and Applied Occupational & Environmental Hygiene.
Two products were also developed through the grant: a dust-wipe sampler to detect lead dust, and an educational card game for parents, on lead reduction strategies.
The Robert Wood Johnson Foundation (RWJF) supported this project with a grant of $445,953 from December 1991 to January 1997. The Environmental Protection Agency (EPA) and the National Institute of Child Health and Human Development also provided funding for the study.
Lead contamination from deteriorating lead-based paint, lead in water tanks and pipes, and other sources is ubiquitous in the inner cities. Much progress has been made in the past two decades in reducing children's lead exposure to lead through lead paint abatement programs targeted at older housing stock. Nevertheless, lead poisoning continues to be a serious health problem with devastating consequences for young children.
While lead abatement programs have had a significant impact on children's direct intake of lead paint, which has been associated with blood-lead levels above 40 ug/dl, there is a growing body of evidence to suggest that much lower blood-lead levels, which were previously thought to be inconsequential, are in fact harmful. Blood-lead levels as low as 15 ug/dl have been associated with mental and physical impairments including reduced cognitive functioning, inhibition of bone growth, poor attention span and verbal processing, and possible hearing impairment.
At the time of this study, the Centers for Disease Control (CDC) was in the process of revising its guidelines to direct public health authorities to note blood-lead levels above 10 ug/dl and institute environmental assessments for children with levels above 15 ug/dl. While one simple source of lead exposure is often not found for children with blood-lead levels between 10 and 30 ug/dl, household dust lead levels are usually the best single environmental correlate in children with those levels.
There are a number of impediments to total lead abatement, chief among them the cost—which can easily run between $7,000 and $15,000 per housing unit—and most of the affected housing is privately owned and controlled. In addition, renters often need to be relocated during total abatement programs. Further, abatement, while it removes the lead paint, can result in increased lead dust unless very careful dust control is maintained. Since it will take decades to abate sources that are found in an individual's home or environment, there is need to develop practical strategies that could be used in the near-term to minimize exposure to young children.
A previous study (Charney, New England Journal of Medicine, 1983) had shown that careful control of lead-contaminated dust after abatement through household cleaning can reduce lead levels by 18 percent in older children who had high blood-lead levels (mean of 40 ug/dl) over a period of one year. This study sought to determine whether similar exposure reduction strategies could be used to decrease blood-lead levels in children with lower levels of exposure.
The project initially had the following four objectives:
- Precisely measure lead content in paint, water, air, and dust samples in the study participants' homes.
- Estimate each child's exposure based on contact with lead from different media (e.g. dust or air) and routes of exposure.
- Identify biological and other markers that can be measured prenatally and in the first nine months of life, and are best able to predict blood lead at two years.
- Test an intervention-exposure reduction program in a randomized trial to examine its capacity to minimize the increase in blood lead that usually occurs in young inner-city children.
The intervention would combine a lead reduction educational program with biweekly help in dust control.
Not long after recruitment efforts began, the project team deleted the third objective with permission of the Foundation. The researchers had initially planned to recruit pregnant women who would enroll their newborn children with the idea that the cleaning protocol could be started when the child was about six months of age.
However, the researchers obtained evidence through some initial sampling of toddlers in Jersey City, N.J., that predicting blood levels at the prenatal stage would not be as successful in identifying children who would truly be at risk of lead poisoning, as would locating toddlers who already had exhibited lead levels between 9 and 20 ug/dl in local blood-screening programs. Recruiting toddlers instead of newborns would also shorten the timeframe needed to complete the study. The study did accept a few children with other indicators that put them at risk, such as an older sibling with elevated lead levels.
Families in and around Jersey City, N.J., were referred by the municipal lead poisoning prevention program or responded to posters and door hangers about the study; 211 were visited by the researchers. Project staff evaluated their homes for the presence of lead paint with a portable x-ray fluorescence detector and conducted a baseline interview, including demographic information and questions that tested the mother's knowledge of lead poisoning and lead sources. The presence of a child between the ages of six months and three years was confirmed. Dust wipe samples were collected from uncarpeted perimeter floor locations in the kitchen and another room frequented by the child. If time permitted, additional samples were collected from interior windowsills. When carpets were present, vacuum sample(s) were collected from those areas thought most likely to be play locations. A baseline venous blood specimen was obtained from the child. Families were provided with basic information about lead poisoning and were invited to continue in the study if they met the following conditions:
- Lead paint in the home or obtained in a composite vacuum dust sample contained more than 0.15 percent lead.
- The home was not in such structural disrepair or so disorganized that it could not be cleaned.
- The home did not evidence illicit drug use or firearms and could be accessed safely by staff.
- The family spoke either English or Spanish.
- The family did not have definite plans to move in the near future.
- Project staff believed the family would be able to cooperate with all of the study procedures.
Families who met these conditions and consented to participate (113) were randomly assigned to a lead-exposure-reduction (intervention) group (56) or to an accident-prevention (control) group (57). Families assigned to the intervention group were asked to cooperate with a cleaning program in which two project staff members, recruited from the community and provided with a short course on appropriate cleaning methods, visited every two weeks to clean up potentially lead-contaminated dust. Floors and carpets were vacuumed with a high efficiency particle accumulating (HEPA) vacuum cleaner and walls, horizontal surfaces, and uncarpeted areas were wet-wiped or mopped with a solution using Spic and Span. Final assessments of lead dust and blood lead in the children were made after one year of intervention.
The families in the accident prevention group (control group) received information regarding lead reduction, however most of their education program focused on preventing accidents in the home. An interactive educational game was also developed on accident prevention. As part of the accident prevention protocol, participants were given home safety items, such as fire extinguishers, smoke detectors, and first aid kits, for their participation. Due to moves out of the area of certain participants, the blood leads were obtained from 99 of the original 113 study children, 46 in the lead intervention group and 53 in the control group. The incentives offered by the project—lead dust control and health education for the intervention group, home safety items for the control group—were an important factor in maintaining participation by members of both groups.
- At the beginning, the dust levels and lead loads were comparable in the intervention and the control groups. Because much more dust is extracted from a carpet than can be obtained from a floor or windowsill, the vacuum loads were much higher than those for the floors and sills. Levels on the sills were higher than those on the floors. At the end of the study, the lead levels were lower for all three locations for the intervention group. While the floor loads did not change much, the carpet and windowsill loads were reduced by 50 percent or more.
- To examine the impact of the dust-lead-control intervention on blood-lead levels, a final blood lead was collected at 12 months (plus or minus 3 months) after the initial blood lead for 46 children in the intervention group and 53 children in the control group. After the intervention, blood-lead levels fell by 2.1 ug/dl (17 percent) in the intervention group and increased by 0.1 ug/dl in the control group.
- Children whose families cooperated fully with the study protocol enjoyed more benefit than did those from less compliant families. Families in the intervention group, whose homes were cleaned 20 or more times, showed an average drop in blood-lead levels of 34 percent. The blood-lead levels did not change for children in homes that had fewer than 10 cleanings.
- The intervention appeared to reduce the chance of sustaining an increase in blood lead. Four intervention-group children and nine control-group children experienced increases of 5 ug/dl during the study period; one intervention-group child and four control-group children experienced increases of 10 ug/dl.
- There was no relationship between the maternal score on a baseline test of knowledge of lead poisoning and the child's initial blood lead or the subsequent change in blood lead. Nor was the number of educational sessions attended by the mother related to the decline in blood lead in the child. However, when knowledge of lead poisoning was assessed at the end of the intervention period, there was a statistically significant increase in knowledge in the intervention group, compared both to the baseline scores and to the control group.
- Recruitment was challenging because it was difficult to identify children who met all the inclusion criteria and parents who were willing to commit the required time. As a result, the overall study size was smaller than the original target of about 150 participants. In addition, in the intervention group, the number of cleaning visits completed ranged from 0 to 42 with a median of 17. The number of health education sessions completed before the final blood lead screening ranged from 1 to 5 with a median of 3 sessions.
- It was not possible to design this trial with separate intervention groups that would have distinguished clearly between the effect of maternal education alone and the effect of maternal education combined with the cleaning protocol.
- About 30 percent of the families moved during the course of the study, some more than once. As a result of these moves, follow-up assessments of blood lead and dust lead was completed for only 85 percent of all participants one year after their initial assessment. The follow-up was somewhat higher in the accident prevention group than in the lead control group, a difference that could be attributed to a few lead group families finding the repeated cleaning visits to be burdensome.
- As implemented, the intervention requires five person-hours per home visit, which, if fully salaried, would be too expensive for most health departments to fund. A somewhat simpler cleaning protocol would have to be developed for it to be incorporated into local public health efforts. As a practical matter, many of the participating families had no vacuum cleaners and some did not have buckets and mops.
- A sampler was developed during this study to collect dust samples and provide a separate quantification of total dust and lead content per surface area. However, this sampler has yielded lower lead-load estimates than the widely used wipe method recommended by the US Department of Housing and Urban Development (HUD) (unpublished observation).
Fourteen articles have been completed and submitted to a number of professional journals and publications. The main paper that presents the study's methodology and findings was completed in 1997 and has been accepted by Pediatrics. Other articles have been published in the Annals of Pediatric and Adolescent Medicine and the Journal of Exposure Analysis and Environmental Epidemiology, and accepted by the American Journal of Preventive Medicine, Environmental Research, and Applied Occupational & Environmental Hygiene. See the Bibliography for details. During the project, a wipe sampler to detect lead dust, and an educational card game on household lead exposure, were patented and are available for distribution.
AFTER THE GRANT
The principal investigator is exploring opportunities for funding that would support replication in other communities and is also refining the articles that were developed from this study and pursuing publication of the study's results in peer-reviewed journals.
GRANT DETAILS & CONTACT INFORMATION
Preventing Lead Exposure in Inner-City Children
University of Medicine and Dentistry of New Jersey - Robert Wood Johnson Medical School (Piscataway, NJ)
Dates: December 1991 to January 1997
George G. Rhoads, M.D., M.P.H.
(Current as of date of this report; as provided by grantee organization; not verified by RWJF; items not available from RWJF.)
Adgate JL, Rhoads GG and Lioy PJ. "The Use of Isotope Ratios to Apportion Sources of Lead in Jersey City, NJ, House Dust Wipe Samples." Science of the Total Environment, 221(23): 171180, 1998. Abstract available online.
Adgate JL, Weisel C, Wang Y, Rhoads GG and Lioy PJ. "Lead in House Dust: Relationship Between Exposure Metrics." Environmental Research, 70(2): 134147, 1995. Abstract available online.
Adgate JL, Willis RD, Buckley TJ, Chow JC, Watson JG, Rhoads GG and Lioy PJ. "Chemical Mass Balance Source Apportionment of Lead in House Dust." Environmental Science Technology, 32: 108114, 1998.
Freeman NCG, Ettinger A, Berry M, and Rhoads G. "Hygiene and food-related behaviors associated with blood-lead levels of young children from lead-contaminated homes." Journal of Exposure Analysis and Environmental Epidemiology, 7: 103118, 1997.
Freeman NCG, Wainman T, and Lioy PJ. "Field Testing of the LWW Sampler and Association of Observed Household Factors with Dust Loading." Applied Occupational and Environmental Hygiene, 11: 476483, 1996.
Goldman KD, Demissie K, DiStefano D, Ty A, McNally K and Rhoads GG. "Childhood Lead Screening Knowledge and Practice. Results of a New Jersey Physician Survey." American Journal of Preventive Medicine, 15(3): 228234, 1998. Abstract available online.
Jobanputra NK, Jones R, Buckler G, Cody RP, Gochfeld M, Matte TM, Rich DQ, and Rhoads GG. Accuracy and reproducibility of blood lead testing in commercial laboratories. Annals of Pediatric and Adolescent Medicine, 152: 548553, 1998.
Lioy PJ, Wainman T, and Weisel C. "A Wipe Sampler for the Quantitative Measurement of Dust on Smooth Surfaces: Laboratory Performance Studies," Journal of Exposure Analysis and Environmental Epidemiology, 3(3): 315330, 1993. Abstract available online.
Lioy PJ, Wainman T, Zhang JJ and Goldsmith S. "Typical Household Vacuum Cleaners: The Collection Efficiency and Emissions Characteristics for Fine Particles." Journal of Air & Waste Management Association, 49(2): 200206, 1999. Abstract available online.
Lioy PJ, Yiin L-M, Adgate J, Weisel C, and Rhoads GG. "The Effectiveness of a Home Cleaning Intervention Strategy in Reducing Potential Dust and Lead Exposures." Journal of Exposure Analysis and Environmental Epidemiology, 8: 1735, 1998.
Rhoads GG, Ettinger AS, Weisel CP, Buckley TJ, Goldman KD, Adgate J and Lioy PJ. "The Effect of a Dust Lead Control on Blood Lead in Toddlers: a Randomized Trial." Pediatrics, 103(3): 551555, 1999. Abstract available online.
Rich DQ, Yiin L-M, Rhoads GG, Glueck DH, Weisel C and Lioy PJ. "A Field Comparison of Two Methods for Sampling Lead in Household Dust." Journal of Exposure Analysis and Environmental Epidemiology, 9(2): 106112, 1999. Abstract available online.
Wang YJ, Rhoads GG, Wainman T, and Lioy PJ. "The Effects of Environmental and Carpet Variables on Vacuum Sampler Collection Efficiency," Applied Occupational & Environmental Hygiene, 10(2): 111119, 1995.
Wang YJ, Willis RP, Buckley TJ, Rhoads GG, and Lioy PJ. "The Relationship Between Dust Pb Concentration and Particle Size of Household Dust Collected in Jersey City Residences." Applied Occupational & Environmental Hygiene, 11: 199206, 1996.
Presentations and Testimony
Adgate JL. "Comparison of House Dust Lead Exposure Metrics Collected by Vacuum and Wipe Sampling Techniques," at the Society for Risk Analysis, 1994.
Ettinger AS. "Reducing Lead Dust in Your Home," at the UMDNJ/SOM Lead Poisoning Prevention Conference, 1994.
Freeman NCG. "Association of Hygiene and Food-Related Behaviors with Blood Lead Levels of Young Children from Lead Contaminated Homes," at the ISEA/ISEE Symposium, 1994.
Freeman NCG. "Field Testing of the LWW Dust Sampler and the Association of Observed Household Factors with Dust Loadings," at the ISEA/ISEE Symposium, 1994.
Wang YJ. "House Dust and Lead Exposure in Preschool Children," at the ISEA/ISEE Symposium, 1995.
Lioy Weisel Wainman Wipe Sampler (LWW), patent pending.
Educational card games available by end of June 1998: Lead Rummy and Accident Concentration.
Report prepared by: Paul Mantell
Reviewed by: Timothy F. Murray
Reviewed by: Molly McKaughan
Reviewed by: Marian Bass
Program Officer: Michael Beachler
Acting Program Officer: Janet Heroux