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Biomedical subjects

R G Tardiff

Publications and source records attributed to R G Tardiff.

At least 19 recordsLinked to original sources
PubMed2001

Weight of evidence for an association between adverse reproductive and developmental effects and exposure to disinfection by-products: a critical review.

Disinfection by-products (DBP) are a side effect of water chlorination. Some toxicological studies suggest an association between DBP exposure and adverse reproductive and developmental effects. This investigation considered all toxicological and epidemiological evidence for the various effects, outcome by outcome. The weight of evidence demonstrated that no association with DBP exposure exists for over a dozen outcomes including low and very low birth weight, preterm delivery, some specific congenital anomalies, and neonatal death. The analysis found inconsistent or very weak results for all congenital anomalies/birth defects, all central nervous system anomalies, neural tube defects, spontaneous abortion, and stillbirth. The weight of evidence suggested a positive association with DBP exposure for some measure of growth retardation (such as intrauterine growth retardation or small for gestational age) and for urinary tract anomalies. Having catalogued these effects, it should be noted that exposure assessment in the epidemiological studies published to date has been inadequate to definitively demonstrate an association of small magnitude. Exposure to DBP primarily has been based on routine (i.e., quarterly) monitoring of public water supplies for trihalomethanes (THM) matched to maternal residence. In order to determine whether an association exists between adverse reproductive and developmental effects and exposure to DBP, studies must consider the THM concentration and the quantity of the water actually consumed by pregnant women.

Abnormalities, Drug-Induced↗
PubMed2000

Carbonless copy paper and workplace safety: a review.

Carbonless copy paper (CCP), introduced in 1954, is ubiquitous in the U.S. marketplace, and because of this, many workers come into contact with it. Its safety to workers who handle large amounts of CCP has been addressed in numerous studies and reports; and the National Institute for Occupational Safety and Health (NIOSH) on two occasions has sought to determine what, if any, hazards to health CCP might pose. This review encompasses the world's literature on CCP and provides a weight-of-evidence analysis of the safety of CCP to workers in the United States. CCP is systematically studied on large groups of humans using repeat insult patch tests. Consistently, CCP in U.S. commerce since 1987 (the focus of this review) has produced neither primary skin irritation nor skin sensitization under exaggerated test conditions, demonstrating that no irritation or sensitization is expected on contact with CCP under normal conditions of manufacture and use. Years after the introduction of CCP, the first case reports appeared in 1974 suggesting an association between CCP use and various generic symptoms. Most of the earliest reports occurred in Sweden in response to negative publicity concerning the product, and to date approximately half of all published articles originate in Scandinavia. Many early reports were questionnaire/interview studies which suffered from suggestive questions, biases, and lack of control for confounding factors. Few studies included a comparison group (i.e., people not exposed to CCP) making it impossible to estimate risk values. Later, sick building syndrome studies, accounting for many relevant factors in the office environment, found no association between CCP exposure and symptoms unexplained by other factors. Animal studies showed that compounds used to manufacture CCP do not have acute toxic potential and are not genotoxic. Finally, very few published complaints have come from the manufacturing sector where the closest and most voluminous contact occurs. A few reports of symptoms have emanated from printing facilities (with a multiplicity of other chemical exposures), but generally most symptoms are reported in the office setting where the exposure is lower than in the manufacturing or printing settings. Based on the weight of the evidence, CCP currently in commerce in the United States is shown not to be the causative agent for the reported general symptoms sometimes associated with it over the years. Recently NIOSH evaluated the literature as to possible hazards to health posed by CCP, and NIOSH is anticipated to conclude that CCP is not a hazard to workers and has only a small possibility of producing mild and transient skin irritation.

Air Pollution, Indoor↗
PubMed1999

Exposure to environmental tobacco smoke in the workplace and the impact of away-from-work exposure.

Concentrating on exposure in workplaces where smoking occurs, we examined environmental tobacco smoke (ETS)-related concentration data from the 16-City Study. This study involved a large population of nonsmokers, used personal monitors, and encompassed a wide selection of ETS-related constituents. This first article in a series of three describes the 16-City Study, considers the impact of demographic variables, and concludes that these variables did not explain differences in exposure to ETS. We compared 16-City Study concentrations obtained in the workplace to previously reported workplace concentrations and determined that data from this study were representative of current ETS exposure in nonmanufacturing workplaces where smoking occurs. Considering factors other than demographic factors, we found that, not surprisingly, the number of cigarettes observed in the workplace had an impact on exposure concentrations. Finally, we compared people from homes where smoking occurs with people from nonsmoking homes and found that people from smoking homes observed more smoking in the workplace and experienced higher concentrations of ETS-related compounds in the workplace, even when they observed the same number of cigarettes being smoked in the workplace. In two subsequent articles in this series, we discuss relationships between various ETS markers and provide estimates of distributions of doses to nonsmoking workers employed in workplaces where smoking occurs.

Adult↗
PubMed1999

Distribution of exposure concentrations and doses for constituents of environmental tobacco smoke.

The ultimate goal of the research reported in this series of three articles is to derive distributions of doses of selected environmental tobacco smoke (ETS)-related chemicals for nonsmoking workers. This analysis uses data from the 16-City Study collected with personal monitors over the course of one workday in workplaces where smoking occurred. In this article, we describe distributions of ETS chemical concentrations and the characteristics of those distributions (e.g., whether the distribution was log normal for a given constituent) for the workplace exposure. Next, we present population parameters relevant for estimating dose distributions and the methods used for estimating those dose distributions. Finally, we derive distributions of doses of selected ETS-related constituents obtained in the workplace for people in smoking work environments. Estimating dose distributions provided information beyond the usual point estimate of dose and showed that the preponderance of individuals exposed to ETS in the workplace were exposed at the low end of the dose distribution curve. The results of this analysis include estimations of hourly maxima and time-weighted average (TWA) doses of nicotine from workplace exposures to ETS (extrapolated from 1 day to 1 week) and doses derived from modeled lung burdens of ultraviolet-absorbing particulate matter (UVPM) and solanesol resulting from workplace exposures to ETS (extrapolated from 1 day to 1 year).

Absorption↗
PubMed1999

Use of environmental tobacco smoke constituents as markers for exposure.

The 16-City Study analyzed for gas-phase environmental tobacco smoke (ETS) constituents (nicotine, 3-ethenyl pyridine [3-EP], and myosmine) and for particulate-phase constituents (respirable particulate matter [RSP], ultraviolet-absorbing particulate matter [UVPM], fluorescing particulate matter [FPM], scopoletin, and solanesol). In this second of three articles, we discuss the merits of each constituent as a marker for ETS and report pair-wise comparisons of the markers. Neither nicotine nor UVPM were good predictors for RSP. However, nicotine and UVPM were good qualitative predictors of each other. Nicotine was correlated with other gas-phase constituents. Comparisons between UVPM and other particulate-phase constituents were performed. Its relation with FPM was excellent, with UVPM approximately 1 1/2 times FPM. The correlation between UVPM and solanesol was good, but the relationship between the two was not linear. The relation between UVPM and scopoletin was not good, largely because of noise in the scopoletin measures around its limit of detection. We considered the relation between nicotine and saliva continine, a metabolite of nicotine. The two were highly correlated on the group level. That is, for each cell (smoking home and work, smoking home but nonsmoking work, and so forth), there was high correlation between average continine and 24-hour time-weighted average (TWA) nicotine concentrations. However, on the individual level, the correlations, although significant, were not biologically meaningful. A consideration of cotinine and nicotine or 3-EP on a subset of the study whose only exposure to ETS was exclusively at work or exclusively at home showed that home exposure was a more important source of ETS than work exposure.

Age Factors↗
PubMed1999

A review of the comparative mammalian toxicity of ethylene glycol and propylene glycol.

The purpose of this article is to review and interpret the scientific literature on the mammalian toxicity of ethylene glycol (EG) and propylene glycol (PG), with the goal of comparing the toxicity of the two chemicals. This type of review may serve as the basis for risk management decision-making. Because EG is not a GRAS (generally recognized as safe) chemical, its uses are restricted when compared with PG; thus, certain routes of exposure are not relevant here for toxicological comparison (e.g., subcutaneous, intramuscular, and intravenous). Therefore, this review is focused on the oral, inhalation, and dermal routes of exposure. However, where toxicological data derived from an alternative route of exposure serve to eludicate mechanisms of toxicity, data from these routes are considered. Based on the review provided herein, the following conclusions can be drawn. From the standpoint of lethality, acute effects, and reproductive, developmental, and kidney toxicity, the toxicity of EG exceeds that of PG. Further, localized dermal effects from EG and PG are both mild, with data suggesting that PG may have a skin contact sensitization potential. Finally, PG exposure in laboratory animals has been associated with reversible hematological changes; no data were located for EG from which to draw a toxicological comparison.

Animals↗
PubMed1997

Risk characterization of methyl tertiary butyl ether (MTBE) in tap water.

Methyl tertiary butyl ether (MTBE) can enter surface water and groundwater through wet atmospheric deposition or as a result of fuel leaks and spills. About 30% of the U.S. population lives in areas where MTBE is in regular use. Ninety-five percent of this population is unlikely to be exposed to MTBE in tap water at concentrations exceeding 2 ppb, and most will be exposed to concentrations that are much lower and may be zero. About 5% of this population may be exposed to higher levels of MTBE in tap water, resulting from fuel tank leaks and spills into surface or groundwater used for potable water supplies. This paper describes the concentration ranges found and anticipated in surface and groundwater, and estimates the distribution of doses experienced by humans using water containing MTBE to drink, prepare food, and shower/bathe. The toxic properties (including potency) of MTBE when ingested, inhaled, and in contact with the skin are summarized. Using a range of human toxic potency values derived from animal studies, margins of exposure (MOE) associated with alternative chronic exposure scenarios are estimated to range from 1700 to 140,000. Maximum concentrations of MTBE in tap water anticipated not to cause adverse health effects are determined to range from 700 to 14,000 ppb. The results of this analysis demonstrate that no health risks are likely to be associated with chronic and subchronic human exposures to MTBE in tap water. Although some individuals may be exposed to very high concentrations of MTBE in tap water immediately following a localized spill, these exposures are likely to be brief in duration due to large-scale dilution and rapid volatilization of MTBE, the institution of emergency response and remediation measures to minimize human exposures, and the low taste and odor thresholds of MTBE which ensure that its presence in tap water is readily detected at concentrations well below the threshold for human injury.

Accidents↗
PubMed1988

Review of interspecies risk comparisons.

Use of laboratory animal data to make quantitative predictions of the risks of toxic effects in humans assumes that a relationship exists between the potencies in animals and humans and that its parameters can be estimated adequately. Such "scaling rules" have been used to predict the risks of carcinogenicity or other effects. A survey of the literature yielded only a modest number of papers devoted to the validity of these interspecies risk extrapolations, of which approximately 25 attempt quantitative comparisons for either radiation or chemical hazards. Some authors have investigated relatively large data sets in an attempt to identify the scaling rule that provides the best correlation of risks in two or more species. Others have selected a scaling rule and investigated whether its predictions from data in laboratory species match the risks found in humans. Opinion is divided on the validity of specific extrapolation rules and the utility of animal experiments for quantitative risk assessment. Correlations exist among risk levels in various species, but many factors appear to influence toxicity that are not captured in a simple scaling rule such as dose per unit weight or per unit surface area. Although scaling rules are useful, better projections will be made if case-specific factors such as pharmacokinetics can be considered. Further careful comparisons of quantitative risk estimates are needed.

Animals↗
PubMed1980

Subchronic oral toxicity of BaCl2 in rats.

Groups of young adult rats of both sexes were exposed to 0, 10, 50, or 250 mg/liter (ppm) of barium as barium chloride in drinking water for 4, 8, or 13 weeks. No adverse effects related to barium ingestion were observed in food consumption, clinical signs, body weight, hematologic parameters (i.e., hemoglobin, hematocrit, red cell count, leukocyte count, prothrombin time, and fibrinogen), serum enzyme activities (i.e., SGOT, SGPT, and blood urea nitrogen), serum ions (i.e., Na, K, and Ca), gross pathology, and histopathology. Water consumption was slightly depressed in the highest dose group. A slight decrease in the relative weight of adrenals of treated vs. control animals was observed. Increasing dose, but not duration of exposure, produced related increases in barium concentrations in liver, skeletal muscle, heart, and bone, with the highest concentrations observed in bone.

Animals↗
PubMed1979

Contaminant levels in animal feeds used for toxicity studies.

Samples of commercial feeds for laboratory rats, guinea pigs, cats, monkeys, rabbits, and hamsters were collected and analyzed qualitatively and quantitatively for selected antibiotics, trace metals, pesticides (organophosphates and chlorinated hydrocarbons), natural agents, and polychlorinated biphenyls (PCBs). The results indicated that antibiotics, parathion, diazinon, aldrin, and the aflatoxins were not detected, whereas, metals, chlorinated hydrocarbon pesticides (except aldrin), and PCBs were continually present. Malathion and estrogen were found occasionally.

Animal Feed↗