Tag: arandano azul cultivo

The results from this study showed that it may be valuable to evaluate the BCF or BAF of CECs in earthworms over time, as there may bean increased potential for biomagnification at a given time point. However, more research is needed to determine if these differences persist for a longer time scale and if they occur in different soils or for other CECs. Out of four major metabolites examined in this study only N4- acetylsulfamethoxazole was quantifiable in the earthworm tissues. N4- acetylsulfamethoxazole was seen to increase to a peak concentration of 4.39 ± 0.4 ng g-1 at 3 d and then decreased to 2.62 ± 0.01 ng g-1 by the end of the 21 d incubation . Further, N4-acetylsulfamethoxazole was also detected in the earthworm soil with the highest concentration observed at 7 d , indicating that earthworms was capable of metabolizing these CECs and excreting the transformation product into its surrounding environment. N4-acetylsulfamethoxazole is the primary metabolite of sulfamethoxazole in humans and has been previously detected in wastewater effluent, environmental samples and plant tissue . However this was, to the best of our knowledge, the first time that N4-acetylsulfamethoxazole has been observed to form in earthworms. The continued observation of the formation of N4-acetylsulfamethoxazole, an acetyl conjugate, in the environment is of considerable interest because conjugates have the potential to maintain the biological activity of the parent compound . Further, because researchers traditionally only quantify parent compounds during environmental assessments,macetas de 10 litros the formation and accumulation of conjugates implies that there may be an underestimation of environmental exposure to CECs such as pharmaceuticals and further incomplete environmental risk assessment of CECs .

This is of particular concern for antibiotics, because of the rise of antimicrobial resistance . The major metabolite of methyl paraben, p-hydroxybenzoic acid, was observed in all soil samples, including the non-treated controls . This was likely due to the endogenous p-hydroxybenzoic acid in sphagnum peat . However, the concentration of p-hydroxybenzoic acid was higher in the spiked earthworm treatments than in the blank controls or non-earthworms chemical controls indicating that E. fetida was also capable of taking up and metabolizing methyl paraben and excreting of p-hydroxybenzoic acid into the soil. This was consistent with previous contact tests in which 70% of the initial methyl paraben was found to be metabolized to p-hydroxybenzoic acid and phenol within 48 h in E. fetida . The transformation products o-desmethylnaproxen and nordiazepam were not detected in earthworm tissues, but o-desmethylnaproxen was quantifiable in earthworm-CEC treated soils during the 21 d incubation , indicating active uptake, metabolism, and excretion. The quantification of the major metabolites for naproxen, sulfamethoxazole and methyl paraben, o-desmethylnaproxen, N4- acetylsulfamethoxazole, and p-hydroxybenzoic acid suggested a trend in the capabilities of E. fetida to take up, metabolize and excrete then transformation products of some CECs in the soil environment. Activities of several vital antioxidant enzymes were determined after exposure to CECs. A significant increase in the activity of glutathione-S-transferase in the treatment samples over the controls was observed starting after 3 d into the incubation , and the GST activity continued to increase until the end of the 21 d incubation . This observation suggested that increased exposure time resulted in increased oxidative stress because glutathione is considered a critical antioxidant that acts to maintain redox homeostasis and signaling in cells . Further, GST is a crucial enzyme family for the detoxification of xenobiotics during Phase II metabolism . Thus, the observed increase in GST activity may indicate that there was a formation of additional Phase II metabolites.

However, the detection of these potential metabolites was not attempted due to a lack of authentic standards. High GST activity was also observed at 0 h for both the controls and treated samples. However, this increase in activity is likely due to the initial stress of the earthworm being transferred into the test media, and the effect dissipated within the first day of exposure. No significant difference in catalase activity was observed between the treatment and controls until the end of the exposure period . At the 21 d time point a significant increase was seen in the treatment samples , indicating that extended exposure to CECs likely resulted in increased production of hydrogen peroxide in earthworm tissue . However, an increase in the CAT activity was also found in the control at 0 h. The increase in CAT activity was, again, likely due to the initial stress of the earthworms being transferred to different environmental conditions and the difference dissipated within 24 h. A significant increase in superoxide dismutase was observed at 1 d and 3 d . However, no significant differences were observed between the treatment and controls after 3 d . This trend was in accordance with SOD has the first line of defense against reactive oxygen species . SOD acts to catalyze the superoxide radical into oxygen molecules or hydrogen peroxide . As an increase in CAT was observed at the later time point it was likely that SOD activity increased initially, resulting in an increased production of hydrogen peroxide, which was then detoxified by CAT. Previous studies examining the biochemical effects of CEC exposure in earthworms showed somewhat similar trends. For example, a study exploring the biochemical and genetic toxicity of triclosan in E. fetida showed a dose-dependent hormesis effect over time for both CAT and GST activity, with increasing activity being observed after a 2 d exposure at low doses and an inhibition of enzyme activity being observed after 14 d at high doses. Further, similar studies considering oxidative stress in E. fetida exposed to herbicides showed an increase in enzyme activities at lower concentrations and a suppression of enzyme activities at high concentrations .Currently we are experiencing a series of global trends that are creating unique challenges for the future of sustainable development. These trends include shifting precipitations patterns, rising temperatures, growing human populations, and rapid urbanization. In order to meet these challenges, traditionally under-utilized resources, such as treated wastewater and bio solids, will have to be harnessed.

These resources are derived from wastewater treatment plants and contain biologically active, pseudo-persistent, trace chemicals referred to as contaminants of emerging concern . Land application of TWW and bio solids for agriculture and landscaping has the potential to introduce CECs into terrestrial ecosystems, from where they could accumulate, be metabolized and/or cause adverse effects in terrestrial organisms. This dissertation has described the ability of terrestrial plants and invertebrates to take up and metabolize CECs and highlighted the potential for these trace contaminants to induce biochemical changes in non-target terrestrial organisms. The findings of this project, overall conclusions, and recommendations for future work are summarized below. In arid and semi-arid areas, TWW reuse is becoming increasingly prevalent for agricultural irrigation. However, irrigation with TWW has the potential to introduce CECs including antibiotics into agroecosystems. One of the most commonly prescribed and environmentally relevant antibiotics is sulfamethoxazole. However, little is known about the fate of sulfamethoxazole in terrestrial plants. In this study, sulfamethoxazole was observed to be taken up and actively metabolized by Arabidopsis thaliana cells into six transformation products. The transformation products included oxidation of the amine group, producing Phase I metabolites, which was followed by conjugations with glutathione, glucuronic acid and leucine, producing Phase II metabolites. Phase III metabolism was assessed by determining the mass balance of 14C-sulfamethoxazole in A. thaliana cells and cucumber seedlings. Non-extractable 14C-sulfamethoxazole increased over time in both A. thaliana cells and cucumber seedlings, indicating that Phase III metabolism significantly contributed to the fate of sulfamethoxazole in A. thaliana cells and cucumbers. Further,macetas de 7 litros in A. thaliana cells and cucumber seedlings, the mass balances were calculated to range from 80-120% and 80-94%, suggesting a minor role of mineralization. The results from this study highlighted the potential of terrestrial plants to transform pharmaceuticals, forming both bio-active Phase I metabolites and Phase II conjugates, and store them as in the form of bound residues as Phase III metabolism. Plant uptake of CECs from TWW reuse and bio-solid application has been documented in agroecosystems. Previous studies suggested that plants were capable of metabolizing CECs after uptake. However, these studies often reported different results even with the same CECs, likely due to the use of different plant species and/or different laboratory conditions. In this study, the metabolism of the benzodiazepine diazepam was explored in three different plant species, A. thaliana, cucumber , and radish . The plants were exposed to diazepam in laboratory under three different laboratory exposure conditions that included a 6 d cell culture, an acute /high concentration hydroponic cultivation, and a chronic /low concentration hydroponic cultivation. 14C-Diazepam was incubated concurrently with non-labeled diazepam to determine the fractions of extractable and non-extractable radioactivity to quantify Phase III metabolism. Diazepam was taken up and metabolized in all plant species under the different exposure conditions. A. thaliana cells actively transformed diazepam into temazepam and nordiazepam via Phase I metabolism.

This metabolism mimicked human metabolism, as temazepam and nordiazepam are the minor and major metabolites, respectively, formed during human metabolism of diazepam. Intriguingly, both of these metabolites are bio-active and prescribed pharmaceuticals in their own right, alluding to a potential for increased risk from consumption not considered in previous studies. The fraction of non-extractable residue increased over the 6 d incubation, indicating extensive Phase III metabolism over time in A. thaliana cells. In cucumber and radish seedlings, a similar Phase I metabolism pattern was observed, with nordiazepam being the most prevalent metabolite at the end of the 7 d and 28 d cultivations. However, significant differences in phase III metabolism were observed between the radish and cucumber plants. For example, after the acute exposure, diazepam mass balance was 99.3% for cucumber seedlings but only 58.1% for radish seedlings, indicating increased mineralization in the radish system. Diazepam induced changes in the regulation of glycosyltransferase activity in both cucumber and radish seedlings, indicating the formation of Phase II metabolites. The results from this study showed that exposure conditions and plant species can influence the metabolism of diazepam, and formation of bio-active transformation intermediates and different phases of metabolism should be considered in order to achieve a comprehensive understanding of risks of CECs in agroecosystems.Exposure of terrestrial invertebrates to CECs will likely increase with increasing TWW reuse and bio-solid application. However, currently there is limited information on the fate and effects of CECs in terrestrial organisms. In this study, the earthworm E. fetida was exposed to three pharmaceuticals, i.e., sulfamethoxazole, diazepam, and naproxen, and one preservative, i.e., methyl paraben, for 21 d in an artificial soil. Methyl paraben did not accumulate in the earthworm tissue, likely due to its rapid degradation in the soil. The other CECs showed an accumulation in earthworm tissues from the soil/soil porewater. The presence of E. fetida did not significantly affect the adsorption of these CECs to the soil. The presence of primary metabolites in the treated soil suggested that E. fetida were capable of actively metabolizing the three pharmaceuticals and excreting the metabolites. However, the metabolism was chemical-specific, and only N4- acetylsulfamethoxazole was detected in earthworm tissues. Exposure to the four CECs also resulted in the up-regulation of several antioxidant enzymes, including glutathione-S-transferase, superoxide dismutase, and catalase, and an increase in malondialdehyde, indicating oxidative stress in the exposed E. fetida. Results from this study highlighted the need to consider the role of, and effects on terrestrial invertebrates when understanding risks of CECs in agroecosystems. Our findings illuminate the complexity of the interactions between contaminants of emerging concern and terrestrial organisms. The dissertation highlights the ability of terrestrial organisms to take up and transform CECs through metabolism, which results in both bio-activation and detoxification of the target contaminants. This project also demonstrates the ability of CECs to alter the biochemistry of the studied terrestrial organisms by changing the regulation of enzymes associated with oxidative stress and metabolism. The use of cell cultivations, hydroponic studies, and artificial soil allowed us to examine the metabolism and effects of CECs in terrestrial organisms with limited confounding factors. However, it is highly likely that similar studies conducted in soils may show low rates of uptake and different patterns in metabolism. Our research suggests that scientifically sound understanding of fate of, and risks from, CECs in the environment cannot solely rely on the assessment of the parent compound and/or only consider the potential for human exposure to CECs.

Infected eggs from these two major egg producers were distributed in fourteen U.S. states, including California. Eggs were recalled using specific plant numbers and codes that allowed tracing back to the box level, leaving no infected eggs in stores.The three egg recalls received extensive national and local media coverage on the television, radio, newspapers, and the Internet. To measure media coverage of the event, we conducted a Lexis-Nexis search, which gave us the daily count of newspaper articles that appeared on the 2010 Salmonella egg outbreak, starting 15 days before the event up to 60 days after the event. Figure 1 shows the number of articles in major newspapers that include the words “Salmonella” and “Eggs” on a given day. Media interest persisted over a six-week period following the event, in particular covering farm inspections that found numerous violations and showed that the egg farms were infested with flies, maggots, rodents and overflowing manure pits, as well as both farm owners testifying before Congress. The fact that there were three consecutive egg recalls within one week could have led consumers to think that this was a major outbreak, and not a regular food recall. Furthermore, given the information provided by the media coverage, some consumers may have obtained information or updated their beliefs on the egg industry as a whole. If consumers were perfectly informed, did not update their beliefs, and expected no further recalls, we could anticipate no effect of the event on consumer purchases. However, if consumers did not have perfect information on the outbreak or the recall codes,macetas de 10 litros updated their beliefs about the egg industry, or “overreacted” to the recalls, we could expect a drop in egg purchases following the event, at least temporarily.

We find that the latter was true.Using a unique product-level scanner data set of a national grocery chain that has stores in both high and low income zip codes, we examine how consumers reacted to the three consecutive egg recalls. First, we test whether consumers changed their egg purchases in California following the recalls. We examine media coverage on the highly publicized outbreak and hypothesize that media coverage is the channel through which consumers became informed about the event. Second, we study whether consumers substitute away from conventional eggs towards other types of specialty “greener” eggs that may be perceived as having a lower probability of Salmonella, such as organic or cage-free eggs. Eggs are currently produced under a variety of methods, but 95% of the national egg production in 2010 came from conventional battery cages. In our California and Washington sample, around 90% of eggs sold came from battery cages. Table 1 summarizes some of the differences between conventional eggs and non-conventional eggs. It is unclear if consumers were aware of the debate in the United States about the link between the type of egg and the probabilities of Salmonella infection. We hypothesize two possible results for purchases of unaffected eggs. On one hand, consumers might substitute away from conventional types of eggs to non-conventional specialty eggs . On the other hand, some consumers might choose to reduce all egg purchases, leading to a decline in purchases of all types of eggs. Third, we investigate whether different socio-economic groups reacted differently to the egg recalls. In particular, we look at whether income and household size affect the response to the recalls. To do this, we use demographic data for the zip code where the store is located. Income may affect the response if wealthier consumers are able to substitute to greener alternatives, which can cost up to twice as much as traditional shell eggs.

Finally, we examine whether separate areas within California reacted differently to the egg recalls. Due to its distribution system, our national grocery chain had infected eggs only in Northern California. We use variation within California to test whether consumers in Southern California reduced egg purchases as well. We use a technique known as differences-in-differences to estimate the effect of the three recalls on egg sales and use a control state that did not receive infected eggs, Washington. We are also able to control for seasonality by using data from previous years around the event date. The differences-in-differences approach consists in comparing changes in egg purchases in affected areas in California to changes of egg purchases in comparable but recall unaffected areas in Washington. If we were to focus only on the changes in California, we could not conclude that those changes were caused by the recalls. We could only show that they are correlated with the recalls. Indeed, other confounding factors, such as macroeconomic conditions, could be responsible for changes in California egg purchases. We net out such factors by using changes for comparable stores in Washington as counter factuals. We use the fact that infected eggs could be traced to the box level to establish a clear definition of the treatment and follow a panel of over 600 stores during a four-year period. Further, given the geographical distribution of infected eggs, we are able to measure potential spillovers to unaffected areas of California.We begin by plotting the evolution of daily sales around the “event week” in California. Figure 2 plots changes in egg purchases for all shell eggs for stores in California only. The category all shell eggs includes 2 classes and 7 sub-classes . The figure plots data starting 30 days before the “event day” up to 35 days after the event day. Changes in egg purchases take into account price, as well as factors that are constant across stores, aggregation levels and day of the week .

Egg sales show a large drop a few days after the first recall and a small increase between the second egg recall and the third recall. Sales reach their lowest level in the time period around 11 days after the first egg recall. This suggests that, if egg purchases decreased due to the egg recalls, there was a small time lag between the time the recalls were made and the time that the effect was reflected in lower purchases in stores. Using our econometric model, we proceed to formally test the effect of the three egg recalls and find a 9% significant reduction in egg sales in California. Given an overall price elasticity for eggs in U.S. households of around -0.1, this sales reduction is comparable to an almost 100% increase in price. Consistent with a rather inelastic demand, the effect is very similar with and without prices. We find that the decrease in sales was driven by a drop in purchases of traditional large shell eggs and find no evidence of substitution toward other greener type of eggs, such as organic or cage-free eggs. More specifically, we find that purchases of large traditional shell eggs significantly decreased by 10% in California in the month following the event. Large traditional eggs had the largest market share of sales in our sample in 2009 . Sales of the other types of eggs do not change significantly due to the recalls. For jumbo, brown, cage-free and nutrient-enhanced eggs , we find no significant effects of the recalls. Sales for extra-large traditional shell eggs and for organic eggs seem higher but the recalls still have no significant effect.When matching each grocery store with the socio-economic characteristics of the zip code in which it is located, we are able to investigate heterogeneous effects of the recall. We study whether income and household size affect the response to the recalls,macetas de 7 litros where income is the demeaned average income in the zip code in which the store is located and household size is the demeaned average household size in the zip code in which the store is located. Socio-economic data come from the 2000 U.S. Census. While we find no correlation with income, we do find that areas that had a larger than average household size decreased egg purchases significantly more. A caveat to the results is that it is possible that more affluent customers diverted egg purchases to farmers’ markets or high-end grocery stores after the egg recalls and thus the estimates would suffer from selection bias. The data allow only for the identification of effects with purchases undertaken at the national grocery chain. We also find differentiated effects among Northern and Southern Californian stores. Although the national grocery chain had infected eggs only in Northern California, we find that Southern Californian stores had lower egg sales as well. The overall sales reduction in Southern California was half as large as the reduction in Northern California, and is consistent with media and reputation effects being significant determinants of demand, even in the absence of an actual food recall. Studies on the effects of safety warnings on spinach , beef or fish have also found significant consumer responses. However, the persistence of the effect may vary depending on the type of good and availability of substitutes. For example, while the effect of a safety warning on spinach had a long-term effect, our results for eggs suggest that the effect was temporary.

To test the robustness of our findings, we perform several checks. First, we test the sensitivity of the baseline results to various assumptions about the seasonality parameters. We use only data for one year before the recall instead of using, as above, all previous years . This yields very similar drops in purchases as when we include all previous years. Second, we test the sensitivity of the baseline results to using Washington as a control state by excluding data from Washington and using stores in Southern California as controls. The rationale is that we may assume that stores in Southern California have similar trends to stores in Northern California. Once again, using Southern California stores as counterfactuals for Northern California store patterns yields very similar estimates of the egg recalls. Third, we test the sensitivity of the baseline results to using only one month after the event week. We obtain data on a second post-event month and include a total of eight weeks after the event week for all years. While this additional robustness check gives us similar results to the ones from the main specification, we find that the effect lasted more than one month.When matching each grocery store with the socio-economic characteristics of the zip code in which it is located, we are able to investigate heterogeneous effects of the recall. We study whether income and household size affect the response to the recalls, where income is the demeaned average income in the zip code in which the store is located and household size is the demeaned average household size in the zip code in which the store is located. Socio-economic data come from the 2000 U.S. Census. While we find no correlation with income, we do find that areas that had a larger than average household size decreased egg purchases significantly more. A caveat to the results is that it is possible that more affluent customers diverted egg purchases to farmers’ markets or high-end grocery stores after the egg recalls and thus the estimates would suffer from selection bias. The data allow only for the identification of effects with purchases undertaken at the national grocery chain. We also find differentiated effects among Northern and Southern Californian stores. Although the national grocery chain had infected eggs only in Northern California, we find that Southern Californian stores had lower egg sales as well. The overall sales reduction in Southern California was half as large as the reduction in Northern California, and is consistent with media and reputation effects being significant determinants of demand, even in the absence of an actual food recall. Studies on the effects of safety warnings on spinach , beef or fish have also found significant consumer responses. However, the persistence of the effect may vary depending on the type of good and availability of substitutes. For example, while the effect of a safety warning on spinach had a long-term effect, our results for eggs suggest that the effect was temporary.