researchers performing testing

The Birth Outcomes and Water (BOW) study is a pilot project assessing the feasibility of conducting research in Nebraska about drinking water quality and health outcomes. BOW is modeled after a large case-control study, the National Birth Defects Prevention Study (NBDPS). A case-control study is an epidemiological study where subjects are classified into one of two groups: Cases (subjects with some condition or disease) or Controls (subjects without the disease). In a case-control study the researchers want to know if the prevalence of an exposure is greater in the cases (the population with the disease) than the controls. The BOW project’s focus is whether adverse birth outcomes in Nebraska are associated with maternal exposure to drinking water containing nitrate and nitrosatable compounds (such as atrazine).

There are many opinions about the health effects of exposure to chemicals used in agriculture. For pesticides researchers typically study people engaged in farming practice and estimate exposure as the number of days the subject applies a specific chemical. Or, exposure is based on residential proximity to farm fields on which the pesticide is applied. For nitrate, exposure is based on exposure through ingestion of nitrate via drinking water or food. Most research examines agricultural chemicals singly. There are very few human studies reporting risk for disease due to exposure to mixtures of contaminants. Sometimes when chemicals are together, they can react to form a more toxic compound than either chemical alone. One example is the mixture of nitrate and atrazine in drinking water. After ingestion, some of the nitrate (NO3) is converted to nitrite (NO2). In the acidic environment of the stomach, the nitrite can react with atrazine, to produce N-nitrosoatrazine (NNAT). NNAT is a nitrosamine. Many nitrosamines are known to cause cancer and developmental defects in animal models. In addition to atrazine, other agrichemicals that can react with nitrite to form a nitrosamine have been detected in Nebraska wells. We call these compounds nitrosatable compounds (NC). Our long term goal is to assess health effects associated with exposure to nitrate and NC in drinking water. The aim of the BOW project is to assess the feasibility of conducting such studies in Nebraska by doing a pilot study to evaluate the risk of adverse birth outcomes associated with maternal exposure to nitrate and NC in drinking water.

Studies like this cannot be conducted without participants. For the BOW pilot project, potential subjects will be identified from the Nebraska Birth and Death Records (NBDR) database. Mothers of a child born between January 1, 2014 and December 31, 2015 will be invited to participate. Information will be obtained from participants through a questionnaire, saliva and blood sample from participants, and drinking water samples from their households.

In addition to its research goals, the BOW pilot project will increase our understanding of what motivates people to participate and identify barriers to participation through voluntary interviews and a focus group.

Sample Size

According to the 2016 Nebraska Vital Statistics Report, the state rate of birth defects (6%) is notably higher than the national rate (3%). Our goal is to explain the higher rate of birth defects in Nebraska. The BOW project is a pilot study, which is a preliminary, small-scale study. BOW will help determine the feasibility of conducting a larger, case-control study about drinking water quality and birth outcomes. An appropriate number of participants (sample size) is required for reliable study results. It is not possible to include the entire population of interest so we use a limited number of subjects from that group. The sample size needed to represent the entire population is determined so conclusions will be valid for the whole group.

One goal of the BOW pilot project is to estimate the sample size needed to conduct the large-scale case-control study. The advantage of using a pilot study first is that it helps to determine the best design for the large-scale study. The BOW pilot project will recruit 40 subjects, which is enough to conduct this preliminary study.

Limitations

Every study has limitations. Limitations of the BOW project might include:

  • Missing data due to withdrawal of some participants. Participants may withdraw from the study due to relocation, death, or lost to follow-up (unreachable) before completing the study. In this case, missing data may cause analytical bias in the results.
  • Collecting blood, saliva and water samples takes time and some may be uncomfortable providing samples: The time required and inconveniences may affect willingness to participate. Some may decline because of the nature of the study.
  • Participants may also change their minds about participating for personal reasons.