Ultimately, addressing the question of population-level effects will likely depend on a combination of measured field data, incorporating new methodologies for assessing survival to adulthood , and fish population models.Our observations must be considered within the constraints of the infrastructure in the Yolo Bypass during the time of our field work. In the intervening years since our field studies, there has been a substantial amount of progress in improving Yolo Bypass infrastructure to support native fishes. During 2017-2018, an inflatable dam fish barrier and collection facility was constructed at Wallace Weir at Knights Landing Ridge Cut . This facility can enhance potential water distribution options for managed flooding studies under relatively low flow conditions when only Yolo Bypass tributary flows are available, including sources from Colusa Basin, which may not always have suitable water quality for juvenile salmonids. It is important to note, however, that these local water sources are not useful unless there is improved connectivity with the Sacramento River, allowing wild juvenile salmon to access seasonal habitat throughout the Yolo Bypass. To that end,fodder growing system the joint Environmental Impact Statement/Report was finalized in 2019 for a project that will improve connectivity between the Sacramento River and Yolo Bypass with a proposed notch in Fremont Weir .
This proposed facility would allow managed flows at lower Sacramento River stages than the current weir structure, thereby increasing the frequency and duration of seasonal inundation, and providing improved access to the floodplain from the Sacramento River fish migration corridor. This upgrade is required as a condition of the 2009 Biological Opinion for Salmonids for long term operation of the federal and state water projects . Our study did not specifically address these new facilities or their operations, and how the concept of managed agricultural floodplain habitat can be integrated into the primary purposes of these improvements. Hence, potential use of flooded agricultural fields as juvenile salmon rearing habitat should be evaluated in light of both a modified hydrology and local land use and infrastructure changes. Additional research is needed to address the efficacy and suitability of different potential water sources, hydrology timing, connectivity with the Sacramento River, and related issues, such as the effects of operations on land use and other species or life stages .Metam sodium, 1, 3-dichloropropene , methyl bromide, and chloropicrin are high use agricultural fumigants that account for about 20% of the annual pesticide usage in California . These fumigants are known respiratory toxicants and were the top four pesticides ranked by chronic health risk based on a risk assessment conducted in the early 2000s . Methyl bromide, 1, 3-DCP and chloropicrin have also been identified as the top three pesticides of public health concern used near schools .
An evaluation of pesticide drift-related illnesses in 11 states found that the largest percentage of cases were related to fumigant applications, indicating the particularly hazardous nature of these substances . Methyl bromide was banned by the Montreal Protocol due to harmful effects on the ozone layer and is currently being phased out of use, resulting in increased usage of chloropicrin, metam sodium and 1,3-DCP in recent years . Cases of acute methyl bromide exposure in adults and children have produced symptoms such as shortness of breath, pulmonary edema, cough, respiratory irritation and respiratory arrest . In the Agricultural Health Study, which examines pesticides and health in a cohort of pesticide applicators and their families, methyl bromide application was associated with higher prevalence of chronic bronchitis in nonsmoking wives of farmers . Metam sodium degrades into methylisothiocyanate, which is known to irritate respiratory tissue , and then further breaks down into methylisocyanate, the active ingredient responsible for the Bhopal tragedy that killed more than 3500 people . In the Bhopal tragedy the most common and serious problems were related to respiratory symptoms . Cases of metam sodium-related illnesses have involved minor respiratory symptoms including coughing and dyspnea . A metam sodium spill in California resulted in persistent respiratoryhealth problems for nearby residents . In a case study of drift from a metam sodium application in California, an association between cases of respiratory illness in nearby residents and proximity to the application area was observed . Increased respiratory symptoms have been reported as a result of community exposure to chloropicrin following application .
A larger analysis of chloropicrin-related illness in California from 1992–2003 found that 54% of cases involved respiratory irritation . Toxicology studies conducted on rodents have shown that 1, 3-DCP exposure is related to benign lung tumor incidence as well as enlargement of the respiratory epithelium. Several epidemiological studies have found an association between occupational exposure to pesticides and an increased risk of respiratory symptoms and asthma . No research to date has been conducted on fumigant exposure and respiratory health in children, who are particularly vulnerable to inhalation risk due to relatively higher inhalation-rate-to-body-weight ratios . There are no biomarkers available to assess human exposure to fumigants in epidemiologic studies . Residential proximity to fumigant use is currently the best method to characterize potential exposure to fumigants. California has maintained a Pesticide Use Reporting system which requires commercial growers to report all agricultural pesticide use since 1990 . A study using PUR data showed that methyl bromide use within ~8 km radius around monitoring sites explained 95% of the variance in methyl bromide air concentrations, indicating a direct relationship between nearby agricultural use and potential community exposure . In the present study, we investigate associations of residential proximity to agricultural fumigant usage during pregnancy and childhood with respiratory symptoms and pulmonary function in 7-year-old children participating in the Center for the Health Assessment of Mothers and Children of Salinas , a longitudinal birth cohort study of primarily low-income Latino farm worker families living in the agricultural community of the Salinas Valley, California.We enrolled 601 pregnant women in the CHAMACOS study between October 1999 and October 2000. Women were eligible for the study if they were ≥18 years of age, <20 weeks gestation, planning to deliver at the county hospital, English or Spanish speaking, and eligible for low-income health insurance . We followed the women through delivery of 537 live-born children. Research protocols were approved by The University of California, Berkeley,chicken fodder system Committee for the Protection of Human Subjects. We obtained written informed consent from the mothers and children’s oral assent at age 7. Information on respiratory symptoms and use of asthma medication was available for 347 children at age 7. Spirometry was performed by 279 of these 7-year-olds. We excluded participants from the prenatal analyses for whom we had residential history information for less than 80% of their pregnancy. We excluded participants from the postnatal analyses for whom we had residential history information for less than 80% of the child’s lifetime from birth to the date of the 7 year assessment. Prenatal estimates of proximity to fumigant applications and relevant covariate data were available for 257 children and postnatal estimates of proximity to fumigant applications and relevant covariate data were available for 276 children for whom we obtained details of prescribed asthma medications and respiratory symptoms. Prenatal estimates of proximity to fumigant applications and relevant covariate data were available for 229, 208, and 208 children for whom we had FEV1, FVC and FEF25–75 measurements, respectively. Postnatal estimates of proximity to fumigant applications and relevant covariate data were available for 212, 193, and 193 children with FEV1, FVC and FEF25–75 measurements, respectively.
A total of 294 participants were included in either the prenatal or postnatal analyses. Participants included in this analysis did not differ significantly from the original full cohort on most attributes, including maternal asthma, maternal education, marital status, poverty category, and child’s birth weight. However, mothers of children included in the present study were slightly older and more likely to be Latino than those from the initial cohort. Women were interviewed twice during pregnancy , following delivery, and when their children were 0.5, 1, 2, 3.5, 5, and 7 years old. Information from prenatal and delivery medical records was abstracted by a registered nurse. Home visits were conducted by trained personnel during pregnancy and when the children were 0.5, 1, 2, 3.5 and 5-years old. At the 7-year-old visit, mothers were interviewed about their children’s respiratory symptoms, using questions adapted from the International Study of Asthma and Allergies in Childhood questionnaire . Additionally, mothers were asked whether the child had been prescribed any medication for asthma or wheezing/whistling, or tightness in the chest. We defined respiratory symptoms as a binary outcome based on a positive response at the 7- year-old visit to any of the following during the previous 12 months: wheezing or whistling in the chest; wheezing, whistling, or shortness of breath so severe that the child could not finish saying a sentence; trouble going to sleep or being awakened from sleep because of wheezing, whistling, shortness of breath, or coughing when the child did not have a cold; or having to stop running or playing active games because of wheezing, whistling, shortness of breath, or coughing when the child did not have a cold. In addition, a child was included as having respiratory symptoms if the mother reported use of asthma medications, even in the absence of the above symptoms.Three identical EasyOne spirometers were used . Routine calibration was performed every morning and 92% of tests were conducted by the same technician. The expiratory flow-volume curves were reviewed by two physicians experienced in pediatric spirometry, and only adequate quality data were included in the statistical analyses. Some participants with adequate quality data for FEV1 did not provide adequate quality data to calculate FVC or FEF25–75. Young children have difficulty sustaining forceful exhalation after a deep breath that is required to produce a plateau in airflow and calculate FVC and subsequently FEF25–75. Each child performed a maximum of eight expiratory maneuvers and up to three best acceptable tests were saved by the spirometric device software. Latitude and longitude coordinates of participants’ homes were collected during home visits during pregnancy and when the children were 0.5, 1, 2, 3.5 and 5 years old using a handheld Global Positioning System unit . At the 7-year visit, mothers were asked if the family had moved since the 5-year visit, and if so, the new address was recorded. We used Geographic Information System software to geocode the new addresses and obtain coordinates. Residential mobility was common in the study population. We estimated the use of agricultural fumigants near each child’s residence using a GIS based on the location of each child’s residence and the Pesticide Use Report data . Mandatory reporting of all agricultural pesticide applications is required in California, including the active ingredient, quantity applied, acres treated, crop treated, and date and location within 1-square-mile sections defined by the Public Land Survey System . Before analysis, the PUR data were edited to correct for likely outliers with unusually high application rates using previously described methods . We computed nearby fumigant use applied within each buffer distance for combinations of distance from the residence and time periods . The range of distances best captured the spatial scale that most strongly correlated with concentrations of methyl bromide and 1,3-DCP in air . We weighted fumigant use near homes based on the proportion of each square-mile PLSS that was within each buffer surrounding a residence. To account for the potential downwind transport of fumigants from the application site, we obtained data on wind direction from the closest meteorological station . We calculated wind frequency using the proportion of time that the wind blew from each of eight directions during the week after the fumigant application to capture the peak time of fumigant emissions from treated fields . We determined the direction of each PLSS section centroid relative to residences and weighted fumigant use in a section according to the percentage of time that the wind blew from that direction for the week after application. We summed fumigant use over pregnancy , from birth to the 7-year visit and for the year prior to the 7-year visit yielding estimates of the wind-weighted amount of each fumigant applied within each buffer distance and time period around the corresponding residences for each child.