When cohort participants were 6 and 12 months old, most households showed signs of moderate or extensive mold at either visit. At age 7, based on maternal report, the majority of families was living below the Federal Poverty Level, 15.7% of cohort children experienced a runny nose without a cold within the past year, 16.3% displayed asthma symptoms, and 6.1% were currently taking asthma medication. Table 2 shows the distributions of wind-weighted fumigant use within 8 km of CHAMACOS residences during the prenatal and postnatal exposure periods. Methyl bromide and chloropicrin were the most heavily used fumigants during the prenatal period, with mean ± SD wind-adjusted use of 13,380 ± 10,437 and 8,665 ± 6,816 kg, respectively. Reflecting declines in methyl bromide use, the use of chloropicrin was greater than the use of methyl bromide during the postnatal period, with median values of 127,977 and 109,616 kg during the 7 years, respectively. When we examined correlations within each fumigant, use within 3, 5, and 8 km from the home was highly correlated for each fumigant . Fumigant use during the prenatal and postnatal periods was also highly correlated for methyl bromide and chloropicrin, but was not correlated for metam sodium use and was inversely correlated for 1,3-DCP use . We also examined correlations among fumigants and observed high correlations between prenatal methyl bromide and chloropicrin use and between prenatal metam sodium and 1,3-DCP use . There were negative correlations between prenatal methyl bromide and chloropicrin use with prenatal metam sodium and 1,3-DCP use .Adjusted associations between a 10-fold increase in the amount of fumigants applied within 8 km of the home and the highest lung function measurements are presented in Table 4. We did not observe any significant adverse relationships between prenatal or postnatal fumigant use within 8 km and lung function. A 10-fold increase in wind-adjusted prenatal methyl bromide use within 8 km was associated with higher FEV1 and FEF25–75 . Additionally, a 10-fold increase in wind-adjusted prenatal chloropicrin use within 8 km was positively associated with FEF25–75 .
Associations between methyl bromide and chloropicrin use and lung function observed in the prenatal exposure period were not observed in the postnatal period. Results were similar, although no longer statistically significant,plastic gardening pots for prenatal methyl bromide and chloropicrin use within 5 km of residences . There were no associations between fumigant use within 3 km of residences and lung function . We did not observe associations between postnatal fumigant use at any distance and lung function measurements or between fumigant use during the year prior to the assessment and lung function measurements . In sensitivity analyses using multivariable models including other pesticide exposures that have been previously related to respiratory symptoms and lung function including childhood urinary DAP metabolites , proximity to agricultural sulfur use during the year prior to lung function assessment and prenatal DDT/DDE blood concentrations , the results were very similar to those presented in Tables 3 and 4. For example, the relationships between prenatal methyl bromide use within 8 km were very similar for FEV1 and FEF25–75 . Prenatal fumigant use was generally not correlated with other pesticide exposures that we found to be associated with lung function in this cohort, except for weak correlations between agricultural sulfur use within 1 km during the year prior to spirometry and prenatal use of metam sodium and 1,3 – DCP with r = 0.14 and r=0.26 respectively. The results were very similar when we only included children with two acceptable reproducible maneuvers in the analyses . The results were also similar when we excluded those currently using asthma medication, excluded the one outlier for FEV1 models or used inverse probability weighting to adjust for participation bias . Risk ratios estimated for asthma symptoms and medication using Poisson regression were nearly identical to the ORs presented in Table 3 and Supplemental Table 2. We did not observe effect modification by asthma medication use. Maternal report of child allergies modified the relationship between FEV1 and prenatal proximity to methyl bromide use and we only observed higher FEV1 among children without allergies .
After adjusting for multiple comparisons, none of the associations reached significance at the critical p-value 0.002 based on the Benjamini-Hochberg false discovery rate. This is the first study to examine lung function or respiratory symptoms in relation to residential proximity to agricultural fumigant use. We found no significant evidence of reductions in lung function or increased odds of respiratory symptoms or use of asthma medication in 7-year-old children with increased use of agricultural fumigants within 3 – 8 km of their prenatal or postnatal residences. We unexpectedly observed a slight improvement in lung function at 7 years of age with residential proximity to higher methyl bromide and chloropicrin use during the prenatal period and this improvement was limited to children without allergies. Although these results remained after adjustment for other pesticide exposure measures previously related to respiratory symptoms and lung function in our cohort, they do not remain significant after adjustment for multiple comparisons. There is a strong spatial pattern of methyl bromide and chloropicrin use during the pregnancy period for our study because of heavy use on strawberry fields near the coast at the northern portion of the Salinas Valley . There could be other unmeasured environmental or other factors that are confounding the relationship we observed between higher prenatal fumigant use and improved lung function. Previously published studies of prenatal exposure to air pollutants and lung function have generally observed links to alterations in lung development and function and to other negative respiratory conditions in childhood, and plausible mechanisms include changes in maternal physiology and DNA alterations in the fetus . Improved lung function was associated with higher estimates of recent ambient exposure to hydrogen sulfide in a study of adults living in a geothermal area of New Zealand . However, hydrogen sulfide has been shown to be an endogenously produced “gasotransmitter”,blueberry pot size with anti-inflammatory and cytoprotective functions , and is being explored for its use for protection against ventilator-induced lung injury .
In previous studies of this cohort, we found increased odds of respiratory symptoms and lower FEV1, and FVC per 10-fold increase of childhood average urinary concentrations of metabolites of organophosphate pesticides . Other studies of prenatal pesticide exposure and respiratory health in children have mostly evaluated exposure using cord blood concentrations of DDE, a breakdown product of DDT, and have observed an increased risk of respiratory symptoms and asthma with higher levels of DDE . Most studies of postnatal pesticide exposure and respiratory health in children have utilized self-reported information from mothers to assess pesticide exposure and have observed higher odds of respiratory disease and asthma with reported pesticide exposure . None of the previous studies of pesticide exposure and respiratory health have specifically evaluated fumigants. Another strength of the study is that CHAMACOS is a prospective cohort followed since pregnancy with extensive data on potential confounders of respiratory health and other measures of pesticide exposure. Our study also had some limitations. We did not have information on maternal occupational exposure to fumigants or the geographic location of maternal workplaces during pregnancy, and we did not have the location of schools during childhood. These limitations likely resulted in some exposure misclassification during both the prenatal and postnatal periods. An important consideration in this study is that we estimated fumigant exposure using proximity to agricultural fumigant applications reported in the PUR data, which is not a direct measure of exposure. However, the PUR data explains a large amount of the variability of measured fumigant concentrations in outdoor air . In conclusion, we did not observe adverse associations between residential proximity to agricultural fumigant use during pregnancy or childhood and respiratory health in the children through 7 years of age. Although we did not observe adverse effects of fumigants on lung function or respiratory symptoms in this analysis, we have seen adverse associations in previous analyses of the CHAMACOS cohort between residential proximity to higher fumigant use and child development. We observed an association between higher methyl bromide use during the second trimester of pregnancy and lower birthweight and restricted fetal growth . We also observed decreases of ~2.5 points in Full-Scale intelligence quotient at 7 years of age for each 10-fold increase in methyl bromide or chloropicrin use within 8 km of the child’s residences from birth to 7 years of age . Future studies are needed in larger and more diverse populations with a greater range of agricultural fumigant use to further explore the relationship with respiratory function and health.
The fact that the annual water used in growing California agricultural products is far greater than the total urban water use is well known . As pressures on water resources intensify globally, there is a growing interest in evaluating the complex ways in which human activities impact the world’s water resources . Globally, the majority of water consumption is used in the production of agricultural products . As a result, the agriculture industry is by far, the most dominant water-using sector. To assess the amount of water used throughout the production and distribution process to produce a final product, researchers have used the term ‘water footprint’, to describe this quantity . Water footprint assessment had emerged as a tool for quantifying consumption of goods and services in one location and the cumulated water use associated with the production of those goods and services in other distant locations . Following the introduction of the water footprint concept, various studies were conducted to quantify global virtual water footprints and assessed virtual water flows between nations , , and . Virtual water flows and water footprint assessments became important elements in evaluating local, national, and global water budgets as reported by Chen and Chen , Duarte et al., , Guan and Hubacek , Hubacek et al. , Velazquez , Yang et al. , Yu et al. , Zhao et al., . Mekonnen and Hoekstra showed that the international virtual water trade in agricultural and industrial products were 2320 billion cubic meter per year in the period 1996-2005, equivalent to 26% of the global water footprint of 9087 Gm3 . noted that although practically, every country participates in the global virtual water trade, few governments explicitly consider assessing virtual water footprint and its impact in their management policies. The majority of the water footprint studies have examined international virtual water footprints between nations . Few have also analyzed the virtual water footprints at a sub-national or state level such as regions within Australia , China , India , and Spain . Within the United States, two studies have been conducted. Fulton et al., reported that California imported more than twice virtual water as it exported and that more than 90% of its water footprint is associated with agricultural products. Mubako et al., quantified virtual water for California and Illinois, and reported that the two states were net virtual exporters in agricultural water trades. Previous studies on virtual water footprints only aimed to quantify the cumulative water footprint required to produce a final product. No study has focused specifically on quantifying the physical water content contained in agricultural commodities and the associated evapotranspiration being exported. The total exported water in agricultural products is distinctively different than the virtual water footprint in that the former is physically exported outside of a geographical boundary, whereas the majority of the water used in quantifying virtual water footprint may remain within the local geographical boundary and be absorbed or reused in some ways. The exported water content in crops is permanently lost and is no longer available for natural hydrologic cycle. This research seeks to fill the gap of knowledge by quantifying the exported water contained in agricultural products and associated induced evapotranspiration. The research also seeks to analyze the energy advantage of applying reclaimed water in crop irrigation, by assessing the carbon footprint reduction and monetary savings for using reclaimed water in arid and semi-arid regions. Fresh water availability has always been the major constraint to growth and development in California.