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Biomedical subjects

P H Howard

Publications and source records attributed to P H Howard.

At least 19 recordsLinked to original sources
PubMed2000

Indoor household pesticides: hazardous waste concern or not?

Many indoor household pesticides are efficient and useful tools for a variety of functions necessary to maintain clean, sanitary, and pleasant homes and institutional facilities, and to provide significant public health benefits. They do so by incorporating active ingredients and formulation technology that have not been associated with significant environmental impact in use or when disposed in landfills. Chemical and environmental fate properties, toxicological characteristics, and use patterns of indoor household pesticides that distinguish them from other categories of pesticides which have been associated with environmental contamination should be recognized when HHW policy is debated and established by governmental agencies. Most indoor household pesticides as defined here should not be considered hazardous waste or HHW because those relatively few containers, often no longer full, that have been disposed with MSW over the years have not been associated with environmental contamination. The tiny amounts of those product residues that will reach MSW landfills have been shown, in general, not to have chemical or environmental fate characteristics that would make them susceptible to leaching. Those that do have the potential to leach based on these characteristics, in most cases, do not represent a threat to human health based on toxicological considerations. However, compounds such as propoxur, which are very mobile and relatively persistent in soil and in addition have been associated with significant potential health effects, may be targeted by the screening process as described here and could be selected for further investigation as candidates for special waste management status (such as HHW). Our analysis and recommendations have not been extended to the many types of lawn and garden pesticides that are commonly used by homeowners and are frequently brought to HHW programs. However, their potential for groundwater contamination could also be judged using the same technical considerations as applied in this review to indoor household pesticides. In light of the very high costs of diverting wastes from the MSW stream and into HHW programs, it is recommended that, as a matter of public policy, all categories of household waste that might be considered as HHW be carefully and objectively evaluated for their potential to harm public health or the environment after disposal at MSW landfills.

Hazardous Waste↗
PubMed1995

Atom/fragment contribution method for estimating octanol-water partition coefficients.

Atom/fragment contribution values, used to estimate the log octanol-water partition coefficient (log P) of organic compounds, have been determined for 130 simple chemical substructures by a multiple linear regression of 1120 compounds with measured log P values. An additional 1231 compounds were used to determine 235 "correction factors" for various substructure orientations. The log P of a compound is estimated by simply summing all atom/fragment contribution values and correction factors occurring in a chemical structure. For the 2351 compound training set, the correlation coefficient (r2) for the estimated vs measured log P values is 0.98 with a standard deviation (SD) of 0.22 and an absolute mean error (ME) of 0.16 log units. This atom/fragment contribution (AFC) method was then tested on a separate validation set of 6055 measured log P values that were not used to derive the methodology and yielded an r2 of 0.943, an SD of 0.408, and an ME of 0.31. The method is able to predict log P within +/- 0.8 log units for over 96% of the experimental dataset of 8406 compounds. Because of the simple atom/fragment methodology, "missing fragments" (a problem encountered in other methods) do not occur in the AFC method. Statistically, it is superior to other comprehensive estimation methods.

Chemical Phenomena↗
PubMed1992

The cytology of pediatric masses: a differential diagnostic approach.

In the United States, fine-needle aspiration biopsy (FNAB) and other cytodiagnostic methods have been underutilized in the evaluation of masses in the pediatric age group. Cytopathologists and cytotechnologists are therefore relatively unfamiliar with the cellular features of lesions that occur in children. On the basis of the cytologic findings from 64 pediatric cases, including 56 FNABs and 8 intra-operative imprints, a differential diagnostic approach to lesions in this age group is presented. The majority of cases can be placed into 1 of 5 cytomorphologic categories: (1) round-cell pattern, (2) mixed inflammatory pattern, (3) spindle-cell pattern, (4) epithelial pattern, and (5) cystic pattern. Once a cytomorphologic category is determined, evaluation for unique cellular features, special studies, and clinical correlation allows a specific diagnosis to be made in most cases. Pitfalls in pediatric cytopathology are illustrated by discussion of the following cases: a renal Burkitt's lymphoma mimicking a Wilms' tumor, a traumatic neuroma masquerading as a recurrent malignant schwannoma, Langerhans-cell histiocytosis resembling granulomatous inflammation, and a cystic granuloma that mimicked a branchial cleft cyst. Consideration of these problems and use of the recommended diagnostic approach will aid in interpretation in this difficult area.

Adolescent↗
PubMed1991

Development of a predictive model for biodegradability based on BIODEG, the evaluated biodegradation data base.

A file of evaluated biodegradation data was used to develop a model for predicting aerobic biodegradability from chemical structure alone. Chemicals were initially divided into three groups: (i) chemicals that degrade rapidly under most environmental conditions without requiring acclimation; (ii) chemicals that degrade slowly or not at all; and (iii) chemicals that are biodegradable, but only after an acclimation period. Chemicals in the first two groups were then used to develop a model for classifying chemicals as rapidly or not rapidly biodegradable. The model is based on linear regression against 34 preselected substructures, and correctly classifies 92% (211 or 229) of the chemicals in the final training set.

Aerobiosis↗
PubMed1991

Fine needle aspiration biopsy of superficial masses in children.

Fine needle aspiration biopsy (FNAB) is an underused diagnostic procedure in children, particularly in the evaluation of superficial masses. A total of 54 FNABs of superficial masses were performed in children aged 1 month to 15 years. Adequate material for diagnosis was obtained in 50 attempts. The cytologic diagnosis increased clinical understanding and provided a guide for treatment in 46 of the 50 cases. The cytologic diagnosis was confirmed in 15 of 19 patients who underwent an operation. Surgical intervention was obviated in 31 patients. There was one false-positive diagnosis of cancer. We describe the role of FNAB in children and its technique, accuracy, and diagnostic problems.

Adolescent↗
PubMed1988

Lactate dehydrogenase activity in cultured neonatal rat heart cells exposed to doxorubicin.

Doxorubicin (Adriamycin, ADR) is an anthracycline antineoplastic with the serious side effect of dose-related cardiomyopathy. A model of ADR cardiotoxicity was created to examine some subcellular toxic effects of ADR with cultured cardiac myocytes (CMCs) exposed to 1 x 10(-7) to 1 x 10(-5) M ADR for 24 to 48 hr. Lactate dehydrogenase (LDH) activity was monitored in the CMC medium to monitor CMC damage as a function of ADR concentration. A four- to eightfold elevation of LDH activity in medium of CMCs exposed to 1 x 10(-6) to 1 x 10(-5) M ADR was found. No change in LDH activity was detected in medium of CMCs exposed to 1 x 10(-7) M ADR or in control CMCs after 24 or 48 h ADR exposure. Data suggest a dose-dependent effect of ADR on LDH activity in CMC medium. Serial monitoring of LDH in media of ADR-exposed CMCs may correlate with other evidence of ADR cardiotoxicity in vitro.

Animals↗
PubMed1985

Activated sludge biodegradation of 12 commercial phthalate esters.

The activated sludge biodegradability of 12 commercial phthalate esters was evaluated in two test systems: (i) a semicontinuous activated sludge test and (ii) an acclimated 19-day die-away procedure. Both procedures demonstrated that phthalate esters are rapidly biodegraded under activated sludge conditions when loss of the parent phthalate ester (primary degradation) is measured.

Journal Article↗
PubMed1984

Shake flask biodegradation of 14 commercial phthalate esters.

An acclimated shake flask CO(2) evolution test was used to study the biodegradability of 14 commercial phthalate esters that are commonly used as plasticizers. Both CO(2) evolution (ultimate biodegradation) and loss of parent phthalate esters (primary biodegradation) were measured. With only a few exceptions, primary biodegradation was 90% or higher, and ultimate biodegradation was in excess of 55% of theoretical results in 28 days. The results showed that all of the commercial phthalate esters were susceptible to biodegradation by mixed populations of microorganisms from natural sources. The results also provide considerable insight into the utility and reproducibility of a standard biodegradation test that is being recommended for widespread screening of chemicals.

Journal Article↗
PubMed1981

Hepatic abscess due to Yersinia enterocolitica without bacteremia.

A 71-yr-old diabetic patient was evaluated because of right upper quadrant pain. He was found to have a large hepatic abscess secondary to Yersinia enterocolitica infection. He lacked clinical evidence of bacteremia or gastrointestinal infection. It is postulated that Yersinia enterocolitica reached the liver through the portal system from an inapparent intestinal infection. This is the first reported case of a liver abscess secondary to Yersinia enterocolitica without evidence of systemic infection.

Aged↗
PubMed1975

Chlorofluorocarbon sources of environmental contamination.

The quantities of chlorofluorocarbons (FCC's) used commercially in the United States and globally are reviewed, and estimates of environmental release from the applications are made. The results indicate that sizable quantities of the FCC's that have been produced have not yet reached the environment and that regulation of U.S. applications would partly reduce, but not end, the possible destruction of stratospheric ozone.

Environmental Pollution↗