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Your Environment. Your Health.

National Survey of Lead & Allergens in Housing (NSLAH)

Closed for Recruitment

Study / Trial Background

We propose to conduct a scientifically valid, descriptive survey to measure the prevalence and levels of lead in dust, soil, and paint, and the prevalence and levels of various indoor allergens in floor and bedding dust in the nation's housing stock. The survey strategy is a population-based, multi-stage area probability sample designed to represent all 50 states. The survey will include approximately 1000 homes in at least 100 primary sampling units (PSU, a metropolitan area or cluster of counties). Residents of candidate participant housing units (HUs) will initially be contacted by a letter to introduce and provide a brief explanation of the study. 

NIEHS in conjunction with the Department of Housing and Urban Development (HUD) Office of Lead Hazard Control sponsored a study entitled the National Survey of Lead and Allergens in Housing (NSLAH). This study provided information to enable HUD and NIEHS scientists to assess the magnitude of the American public's exposure to household indoor allergens. NIEHS conducted the NSLAH in light of recent studies which suggested that cumulative exposure to indoor allergens can increase a person's risk for developing allergic disease and asthma. 

NIEHS is using the allergen data from the NSLAH to: 

  • estimate indoor allergen exposures of the general population 
  • assess the magnitude of levels of indoor allergens in the United States housing stock 
  • evaluate differences in population exposure to allergens based on factors such as region/geography, ethnicity, socioeconomic status, and housing type. 

This study provides important indoor allergen exposure data and seeks to examine the complex relationship between allergic sensitization to indoor allergens and asthma development. 

The questionnaire used in the survey is available as a PDF file: 

National Survey of Lead Hazards and Allergens in Housing: Resident Questionnaire(197KB)

A detailed list of the 75 Population Sampling Units (PSUs) and Strata used in the survey is also available as a PDF file: 

For more information on this study, please visit the Clinical Trials webpage for this study.


The study has completed enrollment. 

  • Ages Eligible for Study: 18 Years to 65 Years 
  • Genders Eligible for Study: Both 
  • Accepts Health Volunteers: No 

Inclusion Criteria: 

  1. The target population for the Survey is the national housing stock of approximately 95 million housing units. 
  2. The decision to include or exclude a subset is usually based on such factors as relevancy to the study objectives, availability of data from other sources, and effort required to obtain the study data. 
  3. None of the possible housing type exclusion or oversampling proposals are based upon gender, race, ethnic, cultural, or biological factors. 
  4. Housing built after 1977. 
  5. Housing units in multi-family buildings. 
  6. Manufactured housing units, i.e., mobile homes and trailers. 

Exclusion Criteria: 

  1. Housing where children are not permitted to live (elderly housing, nursing homes, college dormitories, etc.). 
  2. Group housing - both institutional (prisons or jails, detention centers, hospitals, military housing, etc.) and non-institutional (dormitories, fraternities, orphanages, rooming houses, missions, work camps, convents, etc.). 
  3. Vacant housing. 
  4. Short-term housing. This category includes homes which are not the resident's sole or permanent home, and which the resident present at the time of field data collection spends less than three months per year. This includes seasonal, occasional use, recreational, and second homes, as well as homes for migrant workers. 
  5. Hotels and motels.

What will you do?

Choosing to participate in a study is an important personal decision. Talk with your doctor and family members or friends about deciding to join a study.

What will NIEHS do?

A field interviewer will then visit each candidate HU to screen and recruit eligible units into the study. A short Screening Questionnaire will be administered to an adult HU resident and an invitation will be extended to those HUs that are eligible to participate in the study. A field data collection visit will be scheduled for the following week, at the resident's convenience. The collection visit will be conducted by a two member team (including the same field interviewer that will conduct the screening/recruiting visit) and will consist of administration of an informed consent form and Data Collection Questionnaire, completion of home observation forms, collection of interior dust and exterior soil samples, and conduct of nondestructive paint lead analyses on both interior and exterior walls. Soil and dust samples will be shipped to analytical laboratories for lead and allergen analysis. Extensive survey design, procedure, and reporting details are provided in the National Survey Lead Hazards and Allergens in Housing: Protocol and Sample Design Report. It is anticipated that this study will provide allergen-specific data regarding: 1) housing conditions, demographic factors, and climate to facilitate evaluation of regional, ethnic, socioeconomic, and housing characteristic differences in the indoor allergen burden; 2) an estimate of indoor allergen exposure in the U.S. population; 3) baseline data that can be used as a reference point for future allergen surveys; and 4) a database that can be used to stimulate future studies which attempt to correlate allergen exposure to disease outcome. The study will yield lead hazard data to: 1) estimate the number and percent of homes with dust and soil lead levels above selected thresholds; 2) identify sources of lead in dust in housing; 3) permit future analysis of lead hazard control strategies and costs, including associated policy and regulatory guidelines.

Study / Trial Location

NIEHS Clinical Research Unit (CRU) – Research Triangle Park, North Carolina, USA 27709

Protocol Number: OH98-E-N-33

Enrollment and Contact Information

Additional information can be found at the Sister Study website.

Call toll-free 877-4SISTER

For deaf or hard of hearing, call:

Please use this form to send your question or comments to the Sister Study. Or if you like, e-mail us at; however, be mindful that we cannot protect your personal information sent through email.

Principal Investigator

Darryl Zeldin, M.D.
Darryl C. Zeldin, M.D.
Scientific Director and Principal Investigator
Tel 984-287-3641
Fax 919-541-4214
P.O. Box 12233
Mail Drop A2-05
Durham, N.C. 27709
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