Search

Most agricultural information is reported by government sources on a state or county basis. The purpose of this study was to demonstrate use of geospatial data, the 2002 Agricultural Cropland Data Layer (CDL) for the mid-Atlantic region, to characterize agricultural, environmental, and other scientific parameters for the Chincoteague Bay subbasin using geographic information systems. This study demonstrated that agriculture can be characterized accurately on subbasin and subwatershed bases, thus complimenting various assessment technologies. Approximately 28% of the dry land of the subbasin was cropland. Field corn was the largest crop. Soybeans, either singly or double-cropped with wheat, were the second most predominant crop. Although the subbasin is relatively small, cropping practices in the northern part were different from those in the southern portion. Other crops, such as fresh vegetables and vegetables grown for processing, were less than 10% of the total cropland. A conservative approximation of the total pesticide usage in the subbasin in 2002 was over 277,000 lbs of active ingredients. Herbicides represented the most frequently used pesticides in the subbasin, both in number (17) and in total active ingredients (over 261,000 lbs). Ten insecticides predominated in the watershed, while only small quantities of three fungicides were used. Total pesticide usage and intensity were estimated using the CDL. Nutrient inputs to cropland from animal manure, chemical fertilizer, and atmospheric deposition were modeled at over 30 million pounds of nitrogen and over 7 million pounds of phosphorous. Crops under conservation tillage had the largest input of both nutrients.

In this nested case-control study we examined the relationship between non-Hodgkin's lymphoma (NHL) and organochlorine pesticide exposure. We used a data set originally collected between 1969 and 1983 in the U.S. Environmental Protection Agency National Human Adipose Tissue Survey. Adipose samples were randomly collected from cadavers and surgical patients, and levels of organochlorine pesticide residues were determined. From the original study population, 175 NHL cases were identified and matched to 481 controls; 173 controls were selected from accident victims, and 308 from cases with a diagnosis of myocardial infarction. Cases and controls were mainly from cadavers (> 96%) and were matched on sex, age, region of residence within the United States, and race/ethnicity. Conditional logistic regression showed the organochlorine pesticide residue heptachlor epoxide to be significantly associated with NHL [compared with the lowest quartile: third quartile odds ratio (OR) = 1.82, 95% confidence interval (CI), 1.01-3.28; fourth quartile OR = 3.41, 95% CI, 1.89-6.16]. The highest quartile level of dieldrin was also associated with elevated NHL risk (OR = 2.70; 95% CI, 1.58-4.61), as were higher levels of oxychlordane, p,p'-DDE [p,p'-1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene], and ss-benzene hexachloride (ORs = 1.79, 1.99, and 2.47, respectively). The p-values for trends for these associations were significant. In models containing pairs of pesticides, only heptachlor epoxide and dieldrin remained significantly associated with risk of NHL. Limitations of this study include collection of samples after diagnosis and a lack of information on variables affecting organochlorine levels such as diet, occupation, and body mass index. Given the persistence of pesticides in the environment, these findings are still relevant today.

We used geospatial techniques to study the potential impact of 2 exotic mosquitoes, Aedes albopictus and Ochlerotatus japonicus japonicus, on the epidemiology of West Nile virus in Maryland. These 2 species have established populations in Maryland over the past 15 years. Larvae of both mosquito species are found in natural and artificial water-holding cavities and containers, particularly water in tires. Therefore, we used locations of licensed tire dealers and of tire dumps scheduled for clean up as an index for potential sources of mosquito vectors. This index was expected to underestimate the actual population of source habitats. West Nile virus activity in Maryland during 1999, 2000, and 2001 was indicated by the presence of dead, infected birds, particularly American crows and other corvids; infected pools of mosquitoes; and human and horse infections. Adult females of both mosquito species are aggressive, opportunistic feeders that have been observed to take blood meals from avian and mammalian hosts. Susceptible vertebrate hosts, particularly birds, are ubiquitously distributed throughout the developed areas of the state. This analysis demonstrated a spatial convergence of the virus, the exotic mosquito vectors, and susceptible hosts. This conjunction indicated that these 2 mosquito species have a high potential to serve as bridge vectors and thus, impact the epidemiology of West Nile virus under favorable environmental and climatic conditions. Positive mosquito pools were collected from only the Baltimore-Washington metropolitan corridor, suggesting a newly created enzootic focus for this virus. Land-cover analysis of the sites where virus activity had been detected showed predominantly developed land uses. Analyses of the environmental justice aspects (social, economic, and housing characteristics) of block groups with human West Nile fever cases or with positive mosquito pools were equivocal. Human cases seemed to occur in developed block groups with lower income levels.

Residues of toxic chemicals in human tissues and fluids can be important indicators of exposure. Urine collected from a subsample of the second National Health and Nutrition Examination Survey was analyzed for organochlorine, organophosphorus, and chlorophenoxy pesticides or their metabolites. Urine concentration was also measured. The most frequently occurring residue in urine was pentachlorophenol (PCP), found in quantifiable concentrations in 71.6% of the general population with an estimated geometric mean level of 6.3 ng/ml. Percent quantifiable levels of PCP were found to be highest among males. Quantifiable concentrations of 3,5,6-trichloro-2-pyridinol (5.8%), 2,4,5-trichlorophenol (3.4%), para-nitrophenol (2.4%), dicamba (1.4%), malathion dicarboxylic acid (0.5%), malathion alpha-monocarboxylic acid (1.1%), and 2,4-D (0.3%) were found, but at much lower frequencies. No quantifiable levels of 2,4,5-T or silvex were found. Preliminary analyses showed an apparent relationship between residue concentration and two measures of urine concentration (osmolality and creatinine). A large segment of the general population of the United States experienced exposure to certain pesticides, including some considered biodegradable, during the years 1976-1980.

In December 1990 the U.S. Environmental Protection Agency sponsored a workshop to discuss the applicability of an interim "toxicity equivalency factor" (TEF) approach to assessing risks posed by exposures to complex mixtures of polychlorinated biphenyls (PCBs). The group concluded that application of the TEF approach to PCBs would be less straightforward than it was in the case of chlorinated dibenzo-p-dioxins and dibenzofurans (CDDs/CDFs). It appears that "dioxin"-like properties of some PCB congeners are amenable to a TEF treatment that is compatible with that used for CDDs/CDFs. Such a scheme also seems to have utility in assessing risks to wildlife. Other non-"dioxin"-like toxic endpoints (e.g., neurotoxicity) appear to have a different structure-activity-related mechanism-of-action that requires a separate TEF scheme. The workshop identified data gaps in toxicology and analytical chemistry that hinder adoption of proposed TEF schemes for PCBs at this time.

Halogenated organic compounds are highly lipophilic chemicals that are persistent in the environment as a result of their use and chemical stability. Some of these compounds are also present in the environment as metabolites or oxidation products of a parent compound or as by-products formed in the production of chlorinated compounds. Chronic exposure to the general population results mainly through the food chain. Because they are lipophilic, and because many are metabolized slowly, these chemicals tend to concentrate in body fat tissue. This contribution has described these halogenated organic compounds, discussed their use, regulation and prohibition throughout the world, and reviewed published studies on the levels of these chemicals found in the adipose tissue of humans and animals. For many years, residues of halogenated organic compounds have been detected in the human adipose tissue of individuals in a number of countries, including those in Europe, Asia, and Africa, as well as in the U.S. The levels detected have been used as an index of the level of general population exposure of these compounds over time. Over the past two decades, most countries have observed a steady decline of this level of exposure, reflecting a reduction in the use of these compounds, restrictions on or banning of their use, and a corresponding decrease in their environmental levels. The levels of concentrations vary from chemical to chemical as well as from isomer to isomer. Since the use of aldrin and dieldrin has now been banned or restricted in the U.S. and a number of other countries, residue levels have slowly decreased. Mean values in human adipose tissue in the U.S. and some foreign countries ranged from 0.04 to 0.40 ppm for dieldrin. Aldrin was detected only in Argentina and Poland in the 1970s and endrin was not detected anywhere at anytime. By 1978, all products containing BHC registered in the U.S. has been either discontinued or reformulated to incorporate lindane rather than BHC. The potential for exposure to BHC is virtually nonexistent in the U.S.; however, exposure to lindane is possible since products containing this chemical are still marketed, and used particularly in the manufacture of human medicine. DDT was banned for agricultural purposes in the U.S. in 1972, although it is still used elsewhere for public health vector control. Since the decline in use of DDT, however, the average levels of concentration have also declined. Heptachlor, chlordane, and trans-nonachlor (a component of both heptachlor and chlordane) are chlorinated cyclodienes.(ABSTRACT TRUNCATED AT 400 WORDS)

Mirex is an organochlorine chemical with pesticidal and other industrial usages. Biologically, mirex was used as an insecticide for the control of imported fire ants in large areas of the southeastern United States. Evidence of mirex exposure in a national survey of chemicals in adipose tissue led to a more intensive survey of the general population in treated counties of the southeastern United States. Forty sites were selected randomly from 8 southeastern states where mirex was used widescale to combat fire ants; a total of 624 adipose tissue specimens were collected from these 40 sites. Tissue specimens were prepared by a modified Mills-Onley-Gather procedure and analyzed for mirex and selected other organochlorine compounds by electron-capture gas chromatography. Positive residue findings were confirmed by combined gas chromatography and mass spectrometry. Weighted statistical analysis of the data was conducted to estimate the level of mirex in the study area. It was estimated that 10.2% of the population of southern United States had quantifiable levels of mirex in adipose tissue. The estimated geometric mean of the quantifiable residue amounts was 0.286 ppm (lipid basis). Statistical tests of association and regression were used to investigate possible relationships between the presence and levels of mirex, and the Census Division or state of tissue-specimen collection, by age, race, and sex. These analyses indicated that region or location of tissue specimen collection (assumed to be area of residence) strongly related to both the presence of mirex residue and the amount of mirex residue detected. This may be correlated with the amount of mirex applied for fire ant control or with some other exposure patterns in different regions.

The National Center for Health Statistics collaborated with the National Human Monitoring Program of the U.S. Environmental Protection Agency (EPA) in a four-year study to assess the exposure of the general population to selected pesticides through analysis of blood serum and urine specimens. Specimens were collected on a national probability half sample of persons 12-74 years of age from 64 locations across the United States comprising the sample areas in the Second Health and Nutrition Examination Survey (NHANES II) and analyzed for selected organochlorine, carbamate, chlorophenoxy and organophosphorus pesticides. Medical, nutritional and pesticide usage data are also available for each sample person. Preliminary results of the blood serum and urine analyses indicate that the general population is being exposed to some of these types of pesticides. Since 1970, EPA has conducted a national probability sampling of human adipose tissue. Specimens obtained on a survey design representative of the general population were analyzed for selected organochlorine pesticides and toxic chemicals. Findings from the 1978 survey also indicate exposure of the general population to some of these chemicals. Medical data collected from both surveys have yielded no overt correlations between health effects and residue levels. More intensive statistical analyses are underway to investigate the possible existence of more subtle relationships.

Between September 1973 and February 1974, 57 samples of human milk were collected from women residing in selected areas of Arkansas and Mississippi. Residues of p.p'-DDT, p.p'-DDE, p.p'-TDE, beta-BHC, dieldrin, heptachlor epoxide, oxychlordane, and trans-nonachlor were measured by electroncapture gas chromatography; trace amounts of o,p'-DDT and polychlorinated biphenyls were also detected. Additional analytical procedures were employed to confirm the presence of specific residues.

Chlordane was, prior to regulatory action by EPA in 1976, an extensively used insecticide for both household and agricultural pest control purposes. It was readily available to the general public for many years; thus, human exposure, including poisonings, has been documented. A case reporting fatal chlordane ingestion with residue levels in various body tissues is presented. Analyses were performed by gas-liquid chromatography. The highest residue levels were reported in stomach contents, liver, brain, and adipose tissue.

The racial stratification of residues of total DDT equivalent, heptachlor epoxide, oxychlordane, dieldrin, beta-benzene hexachloride and lindane in human adipose tissue was studied. Samples of human adipose tissue were obtained from locations selected in the contiguous United States according to a stratified, proportionate-random survey design and chemically analyzed for selected organochlorine pesticides. The most marked case of racial difference in residue level was total DDT equivalent. Samples from Negros contained almost twice as much of this chemical as did samples from Caucasians. Racial stratification also was found in the frequency of lindane. Lindane was detected about twice as often in samples from Negros than in samples from Caucasians. Little racial differences were noted for residues of beta-benzene hexachloride, heptachlor epoxide, dieldrin and oxychlordane.

Uses of pesticides and related agrochemicals have been regulated in the United States since 1948. The United States government has supported human and environmental monitoring for pesticides and selected toxic chemicals for the past 15 yr. The initial ambient monitoring systems were designed to determine average concentrations of pesticides and related chemicals in human and environmental media on a nationwide basis and determine changes in these concentrations over time. The results of these surveys showed that almost all of the general human population and various environmental components contained low concentrations of chlorinated pesticides. As the Environmental Protection Agency (EPA) restricted many uses of the chlorinated pesticides, the organophosphorous and carbamate pesticides which replaced them were not as easily monitored by ambient surveys. Special monitoring studies had to be done more frequently to produce data on these compounds which were not as persistent or accumulative in the environment. Currently, a re-evalution has begun to determine pesticide monitoring data needs for the next 5 to 10 yr, modify existing ambient surveys, and plan needed short-term studies to efficiently meet regulatory data needs. Ambient monitoring for trends in chemical levels in humans and the environment will continue in the United States at a reduced level, and many exposure data needs will be met with use-specific monitoring studies.

Agricultural uses of the insecticide DDT were cancelled by the U.S. Environmental Protection Agency December 31, 1972. However, the domestic use of DDT had begun to decline before this action. Beginning July 1969, residues of DDT and its metabolites were measured in human adipose tissue collected through an annual national survey. Levels of total DDT equivalent residues in human adipose have decreased slightly, but the frequencies of finding DDT or its metabolites have remained high. The most marked decline in residue concentration has been found in the youngest age group (0-14 years). Approximately 80 percent of the total DDT equivalent found in this survey was DDE. These data show that the reduction of the agricultural uses of DDT has decreased human exposure to and storage of this chemical.

Hexachlorobenzene (HCB) is a chemical of concern to the US Environmental Protection Agency. Although the use of HCB as a fungicide has virtually been eliminated, detectable levels of HCB are still found in nearly all people in the USA. This paper describes an examination of HCB-residue levels from the US National Human Adipose Tissue Survey, which is an annual programme to collect a nationwide sample of adipose-tissue specimens and analyse them for the presence of toxic compounds. The specimens are collected from surgical patients and autopsied cadavers according to a multistage statistical survey design that allows identification of geographic and demographic subpopulations with elevated HCB levels, and thus may help to indicate sources of human exposure to this chemical. Data on HCB body-burden levels are available for the years 1974-1983, excluding 1980 and 1982. The estimated average residue level of 6115 specimens is 0.053 ppm, the ninetieth percentile value is 0.09 ppm and the range is 'not detected' to 4.33 ppm. The analysis reveals that while the percentage of individuals with detectable levels is increasing, the annual average level is decreasing. A large percentage of specimens with elevated HCB levels comes from the Pacific census division and the oldest age group. In comparison, world-wide detectable levels are approaching 100% and average residue levels tend to increase with age. World-wide HCB levels are higher in females, which contrasts with findings from the National Human Adipose Tissue Survey.

A case of fatal suicidal ingestion of diazinon insecticide is presented. Diazinon concentrations in post-mortem body fluids and tissues were determined using electron capture and flame ionization gas-liquid chromatography. The highest concentrations of diazinon were found in blood, stomach contents, bile and adipose tissue.