Data collection in RFTS involved two primary components: 1) collection of
individual level information about RFTS participants and their pregnancy obtained through interviews, an early pregnancy ultrasound, medical record abstraction and vital records matching, and 2) collection of information on DBP concentrations in the water distribution systems serving the three study sites while RFTS participants were pregnant. The following sections discuss these components in detail.
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3.4.1 Collection of individual information on RFTS participants
Figure 2 summarizes the sources and timing of individual level data collection over the course of RFTS, beginning with the screening interview through collection of birth outcome information. These sources of data are described in detail below.
Figure 5. Flow diagram of data collection
Screening interview
A 5-minute telephone screening interview was conducted with interested women, at which time information necessary to establish eligibility was collected (e.g., maternal date of birth, residential address, and LMP). In addition, if a woman was found eligible and agreed to enroll in the RFTS study, staff completed a 5 to 10-minute interview at screening to collect personal information about the participant. This included information on race/ethnicity, marital status, and education level.
63 First trimester ultrasound
First trimester endovaginal ultrasounds were conducted by clinical sonographers required to have ARDMS® certification, use state-of-the-art equipment as assessed by a study investigator (KH), conduct and document manufacturer recommended machine calibration, and have three or more years experience in pelvic and obstetric diagnostic sonography. In addition, sonographers participated in study-specific training. Measurements of the gestational sac, yolk sac, fetal pole, and fetal heart rate were fully comparable with those required for clinical pregnancy dating. A still image was reviewed by trained staff prior to entry of ultrasound data, and a 20% quality sample was reviewed by a clinician skilled in first trimester sonography (KH). All ultrasounds were performed at or before 13 weeks’ completed gestation (mean= 9 weeks, median = 8 weeks).
Baseline telephone interview
The baseline telephone interview was completed 1 to 2 weeks after enrollment and no later than 16 completed weeks’ gestation. A contract research organization (Battelle) conducted the baseline interviews. The baseline interview took on average 45 minutes to complete. Phone numbers and best times to call were obtained during the screening interview and provided to Battelle. The interview covered the following topics:
• Demographic information: social, household, and income information
• Recent/Current employment
• Health behaviors
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• Menstrual history
• Previous pregnancy history, time to conception, current pregnancy history • Physical and sexual abuse
• Vitamin and mineral supplement use
If a participant had a pregnancy loss prior to completing the baseline interview, she completed a modified version of the baseline interview. If a participant did not complete the baseline interview by 16 completed weeks’ gestation, she was not contacted to complete the follow-up interview 26.
Follow-up telephone interview
The follow-up interview was completed with participants starting at 20 weeks’ gestation. RFTS attempted to complete the follow-up interview during week 20 when possible, and all follow-up interviews were completed no later than 25 weeks’ gestation. Battelle also conducted the follow-up interview, which lasted 30 minutes on average. This interview covered the following topics:
• Changes in water use habits and health behaviors
• More information on previous pregnancy history and current pregnancy history, including pregnancy-related symptoms and information on prenatal care/delivery choices
• Maternal medical history
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A participant completed the modified follow-up interview if she had a pregnancy loss before she was called to complete the follow-up interview 26.
Collection of live birth outcome information
Information on birth outcomes was collected from three sources: medical records, vital records and participant self-report. For pregnancies ending in a live birth between 2001 and 2003, RFTS staff first attempted to obtain key information on pregnancy outcome from vital records (i.e., date of delivery, birth weight and infant sex). For those women who gave birth in 2004 and for whom vital records could not be successfully matched, RFTS requested hospital discharge summaries and prenatal care records to abstract birth outcome
information. Information abstracted from medical records included:
• Infant date of birth (DOB), birth weight and gender
• Apgar scores at 1 and 5 minutes
• Congenital anomalies
• Delivery methods
• Indication for preterm birthFinally, self-reported information on live birth outcomes was also obtained verbally from some participants during a follow-up telephone call or from a short 1-page questionnaire mailed to participants, which the participant then completed and mailed back to the RFTS office. Of note, outcome information is available from multiple sources for some participants (e.g., medical records and self-report). In this case, information was taken from medical records first, vital records second and participant self-report last.
66 3.4.2 Collection of data on DBP concentrations
The following section describes how data on DBP concentrations was collected and analyzed. In addition, results are presented from a small validation study to confirm the lack of spatial variation in THM and HAA concentrations at the chlorinated and brominated DBP sites.
Determining sampling points
Utility companies were visited by a RFTS team member at the beginning of the study to review the water treatment facilities (including the method of terminal disinfection), analyze the service area and distribution system, select possible sampling locations, and collect samples at a number of locations for DBP analysis. Using information collected from the initial sampling trip, a representative sampling location was chosen for each utility for the remainder of the study. Because Site 3 had several booster chlorination stations serving a large portion of its population, two sampling locations were chosen at the brominated DBP site: 1) the treatment plant point of entry (POE) to the distribution system and 2) a second location on the downstream side of a booster station. The amount of chlorine applied at the booster station was relatively minor (0.3 to 0.5 mg/liter), so it was expected that the added free chlorine would be converted by residual free ammonia in the water to combined chlorine with little additional formation of DBPs 26.
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As part of the RFTS study, weekly water samples were collected at the representative locations for the chlorinated and brominated DBP site. Samples were collected every other week at the low DBP site. Residual chlorine concentrations and temperature were also measured at the time of DBP sample collection. The chlorinated DBP site utility system switched from combined chlorine to free chlorine for one month each year (March) to control potential microbial re-growth and biofilm problems. To account for the anticipated spatial variation in DBP levels during the one-month conversion, samples for DBP analysis were collected weekly at up to 10 locations in the distribution system. The brominated DBP sire utility also converted to free chlorine for a period of several weeks during October 2003. Again, samples were collected weekly at a number of locations in the distribution system including the representative sample locations to account for the anticipated spatial variation in DBP levels 26.
Collection of water samples was performed by field personnel in accordance with a specified protocol. Key features of the protocol are listed below:
• Sample collection vials were washed, labeled, and reagents added prior to shipment to study sites.
• Identification labels indicating the sampling location, target analyte, reagents added were placed on all vials; samplers also recorded the date/time of sample collection and their initials on the label.
• Chain of Custody documentation and return overnight shipping labels were included with each shipment of vials.
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• Weekly THM and HAA samples at moderate DBP sites and bi-weekly sample at the low DBP site were collected in quadruplicate in order to provide duplicate samples for analysis and for matrix spike analyses.
• Samples were collected near mid-day on Thursday at the chlorinated DBP site, Tuesday at the low DBP site, and Wednesday at the brominated DBP site from a cold-water tap that had been run for at least five minutes prior to sample collection.
• The samples were returned by overnight delivery to the Drinking Water Research Center laboratories of UNC where they were inspected and stored in a refrigerator at 4oC.
• A tracking database which included information on sampling date, target analyte, outgoing shipment date, date received back at UNC, extraction date, instrument analysis date, quantification date, and quality control review status was kept at the University of North Carolina.
Please see appendix 1, “Water Sampling Methodology” excerpted from Savitz et al. (2005) for the full protocol.
Analysis of THM concentrations
THM samples were analyzed within a 14-day holding time of the sample collection date using a 5890 series II gas chromatograph (Agilent Technologies, Palo Alto, CA) equipped with an electron capture detector. A modified version of EPA Method 551.1 104 was utilized to extract each of the THM4 species from the aqueous samples (see appendix 1 for full details). The practical quantification limit (PQL) for all THMs was 0.1
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micrograms/liter. Linear calibration for each THM species was in the range of 1.0-150
micrograms/liter. The acceptable relative percent difference for THM analysis duplicates was <10% and the matrix spike recovery had to be in the range 80-120%. Any samples not meeting these criteria were flagged and examined further for analytical or instrumentation errors 26.
Analysis of HAA concentrations
HAA samples were analyzed within a 21-day holding time using a 5890 series II gas chromatograph (Agilent Technologies, Palo Alto, CA) equipped with an electron capture detector. The method used for extraction of all nine HAA species was developed by Brophy et al. 105 and based upon EPA method 552 106 and Standard Method 6251B 107 (see appendix 1 for full details). The coefficient of variation (% CV) was calculated for the surrogate area counts of all analytical samples. The PQL was 1.0 or 2.0 micrograms/liter, depending on the HAA, and the maximum calibration standard utilized was 150 micrograms/liter. Analysis and quantification of the calibration standards and aqueous samples was based on replicate precision of duplicate samples having a relative percent difference of less than 25 percent 26.
Analysis of TOX concentrations
TOX analysis was performed using a model AD-2000 Adsorption Module and TOX Analyzer (Tekmar Dohrmann, Cincinnati, Ohio). Samples of 250 milliliters were acidified to pH < 2 with 2 milliliters of concentrated sulfuric acid (H2SO4), loaded into an adsorption module, dispensed through two granular activated carbon columns, and subsequently rinsed
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with potassium nitrate to remove retained inorganic chloride. The carbon was then combusted at 850°C to volatilize organic halogens, which were then analyzed by micro- coulometric detection. Preceding and following each batch of samples, a “nitrate blank” was also analyzed to determine the contribution of background organic halogen from the
reagents, carbon, and carrier gases. TOX concentrations (in micrograms chlorine/liter) were calculated by adding organic halogen for the combustion of top and bottom columns of samples (in micrograms chlorine), subtracting the average of nitrate blank concentrations, and then dividing by volume (in milliliters) of sample absorbed.
Table 14. Distributions of DBP concentrations by study site
DBP concentration (µg/liter)
Location n Mean Median Maximum Minimum
Chlorinated DBP Site THM4 177 63.3 60.7 149 24.7 CHCl3 177 45.6 43.5 124 14.7 CHBrCl2 177 13.8 12.5 33.3 6.8 THM-Br 177 17.8 16.2 43.5 9.0 HAA5 177 33.2 31.9 62.2 12.1 HAA9 177 43.2 41.5 78.9 15.4 HAA-Br 177 10.8 10.2 28.7 1.9 Brominated DBP site THM4 108 58.9 57.8 165.0 26.6 CHCl3 108 11.5 10.0 52.7 3.0 CHBrCl2 108 19.0 18.3 51.7 7.1 THM-Br 108 47.4 44.9 112.3 21.4 HAA5 108 21.5 20.1 53.1 13.2 HAA9 108 45.8 44.7 98.9 30.4 HAA-Br 108 32.0 31.4 55.7 20.4 Low DBP site THM4 157 4.2 3.6 15.9 1.4 CHCl3 157 BMRL BMRL 2.4 BMRL CHBrCl2 157 1.5 1.1 6.5 BMRL THM-Br 157 3.9 3.4 13.5 1.4 HAA5 157 BMRL BMRL 3.1 BMRL HAA9 157 3.5 3.3 6.5 BMRL HAA-Br 157 BMRL BMRL 6.4 BMRL
BMRL=below the minimum reporting level (i.e., “non-detects”) Table adapted from Savitz et al. 2005 AWWARF report
71 Measured THM and HAA concentrations
Table 14 presents the mean, median, maximum and minimum concentrations of select THM and HAA species over the respective periods when water sampling was conducted at each site. Overall concentrations of TTHM and HAA5 were similar at the chlorinated and brominated DBP sites; however, relative concentrations of chlorinated and brominated THM and HAA species varied markedly between. THM and HAA concentrations were much lower at the low DBP site than at moderate DBP sites. Of note, marked seasonal variation in THM levels was observed in the chlorinated DBP site and to a lesser extent at the brominated DBP site, with peak concentrations occurring in summer months and lower concentrations in winter months 26.
Validation of sampling strategy
The proposed sampling strategy described above was confirmed by validation studies conducted at chlorinated and brominated DBP sites. Water samples were collected from six sampling locations within each water distribution system on the same day. Apart from concentrations at the point of entry (POE) to the distribution system, measurements of TTHMs at the chlorinated DBP site were all similar, ranging from 51 to 57 micrograms/liter (figure 3). The POE value (labeled HRT = 0 in figure 3) is lower than the others because the sample was taken before the ammonia was fully mixed into the finished water. TTHM levels were also similar at the brominated DBP site, ranging 89 to 99 micrograms/liter (figure 4). These results, which were repeated on two other occasions at the chlorinated DBP site and one other occasion for the brominated DBP site, confirm that there was very little spatial variation in THM concentrations in the water distribution systems serving the moderate DBP
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sites. Similar consistency in HAA concentrations was found on multiple occasions at the moderate DBP sites (results not shown) 26.
Figure 6. Spatial variability of THM species at the chlorinated DBP site, February 2003
0 10 20 30 40 50 60 0 14 19 20 27 34 52 HRT (hours) Co nc ( g/ L) CHBr3 CHBr2Cl CHBrCl2 CHCl3
Figure 7. Spatial variability of THM species at the brominated DBP site, June 2003
0 20 40 60 80 100 120 A B C F G H I Sampling Location C onc ( μ g/ L) CHBr3 CHBr2Cl CHBrCl2 CHCl3
Abbreviations: Conc = concentrations, HRT = hydraulic residence time Adapted from Savtiz et al. (2005) AWWARF report
Abbreviations: Conc = concentrations
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