Ronald G. Menton

Aggregate exposures of nine preschool children to persistent organic pollutants at day care and at home

In the summer of 1997, we measured the aggregate exposures of nine preschool children, aged 2–5 years, to a suite of organic pesticides and other persistent organic pollutants that are commonly found in the home and school environment. The children attended either of two child day care centers in the Raleigh–Durham–Chapel Hill area of North Carolina and were in day care at least 25 h/week. Over a 48-h period, we sampled indoor and outdoor air, play area soil and floor dust, as well as duplicate diets, hand surface wipes, and urine for each child at day care and at home. Our target analytes were several polycyclic aromatic hydrocarbons (PAH), organochlorine pesticides, and polychlorinated biphenyls (PCB); two organophosphate pesticides (chlorpyrifos and diazinon), the lawn herbicide 2,4-dichlorophenoxyacetic acid (2,4-D), three phenols (pentachlorophenol (PCP), nonyl phenols, and bisphenol-A), 3,5,6-trichloro-2-pyridinol (TCP), and two phthalate esters (benzylbutyl and dibutyl phthalate). In urine, our target analytes were hydroxy-PAH, TCP, 2,4-D, and PCP. To allow estimation of each childs aggregate exposures over the 48-h sampling period, we also used time–activity diaries, which were filled out by each childs teacher at day care and the parent or other primary caregiver at home. In addition, we collected detailed household information that related to potential sources of exposure, such as pesticide use or smoking habits, through questionnaires and field observation. We found that the indoor exposures were greater than those outdoors, that exposures at day care and at home were of similar magnitudes, and that diet contributed greatly to the exposures. The childrens potential aggregate doses, calculated from our data, were generally well below established reference doses (RfDs) for those compounds for which RfDs are available.

Monitoring methods for polycyclic aromatic hydrocarbons and their distribution in house dust and track-in soil

An analytical method was developed and employed to determine polycyclic aromatic hydrocarbons (PAH) in house dust and soil. The method was applied to the analysis of samples collected in an eight-home pilot study that was conducted in Columbus, OH, before and after the 1992/1993 heating season. The purpose of the study was to obtain concentration profiles of PAH in house dust and track-in soil, and to determine whether the track-in of outdoor soil contributes to PAH in house dust. A total of 19 PAH, ranging from naphthalene (2-ring) to coronene (7-ring), were monitored. The sums of concentrations of the 19 PAH ranged from 16 to 580 ppm (w/w) in house dust, from 58 to 5500 ppm in entryway soil, from 0.58 to 1200 ppm in pathway soil, and from 0.63 to 63 ppm in foundation soil. In general, the concentration trend was as follows : entryway soil > house dust > pathway soil > foundation soil. PAH levels in house dust and track-in soil were of the same order of magnitude before and after the heating season. In house dust samples, levels of most 4- to 6-ring PAH, the sums of the 19 PAH, and the sums of the PAH that are probable carcinogens correlated well (r > 0.90 at p < 0.001) with the corresponding levels in the entryway soil samples.

Efficacies of Atropine/2-PAM and Atropine/HI-6 in Treating Monkeys Intoxicated with Organophosphonate Nerve Agents

The efficacies of atropine (ATR)/ 2-PAM and ATRl HI-6 in treating male rhesus monkeys injected with the neurotoxic organophosphonate (OP) agents GA, GB, GD, GF, or VX were compared. Experiments were conducted using no more than 8 monkeys per OP and treatment regimen. Doses were selected using a modified up-and-down experimental design, challenging one monkey per day per OP and treatment. Results were used to approximate the median lethal dose (MLD) for groups of treated monkeys or monkeys given only a vehicle following challenge with an OP. Mortality and signs of intoxication with each treatment were statistically compared. Doses of 2-PAM (25.7 mgl kg) or HI-6 (50 mgl kg) and atropine (0.4 mg free base! kg) were given in a single intramuscular (IM) injection 1 min following challenge with an OP. Strong and well-defined relationships between agent dose and 10-h lethality were observed in untreated animals. The 10-h IM OP MLDs for untreated monkeys were estimated to be 80, 43, 8.0, 22, and 7.4 μg/kg for GA, GB, GD, GF, and VX, respectively. No statistical differences w ere found between AT Rl 2-PAM and AT Rl HI-6 treatment efficacies in preventing lethality for any of the OPs. Both oxime combinations appear to provide protection against a 2 × 10-h MLD of GA, GF, or VX; only

Neuromuscular Effects of Low Level Exposures to Sarin, Pyridostigmine, Deet, and Chlorpyrifos

A study is being initiated to investigate subtle neurobehavioral effects and neuropathology in rats due to exposure to combinations of low levels of Sarin (GB), N,N-diethyl-m-toluamide (DEET), chlorpyrifos (CPF), and pyridostigmine bromide (PB). A similar study is being initiated in rhesus monkeys to investigate neurophysiologic effects and neuromuscular pathology due to exposure to a combination of GB, DEET, CPF, and PB, along with vaccination with botulinum toxoid. A description of these studies is presented.

Comparative Efficacy of three Methemoglobin Formers in Delaying Effects of Infused Sodium Cyanide

A prophylactic treatment is needed to circumvent constraints of the current therapy for cyanide (CN-) intoxication: intravenous administration of sodium nitrite and sodium thiosulfate. Experiments were conducted to compare the anticyanide effects of three candidate pretreatment methemoglobin (MHb)-forming compounds in an anesthetized animal model. The experiment was conducted in 5 periods, with each of 9 animals receiving the vehicle control in period 1, 0.2 mg/kg p-aminopropiophenone (PA PP) in period 2, and 2.5 mg/kg WR242511 in period 3. Four of the animals received the vehicle control in period 4 followed by 7 mg/kg p-aminoheptanophenone (PA HP) in period 5, and 5 animals received 7 mg/kg PA HP in period 4 followed by the vehicle control in period 5. Sodium cyanide (Na CN) infusions for PAPP, PAHP, and WR242511 experiments were initiated when the predicted MHb level was approximately 5%. Infusions were stopped 10 s after no functional breaths (respiratory arrest) were observed. Blood samples were collected for hemoglobin (Hb), MHb, and total blood CN levels at scheduled time points. Time to respiratory arrest, percent MHb, and Na CN dose were the primary response parameters. A 11 pretreatment regimens effectively mitigated the effects of Na CN poisoning compared to the vehicle control (p <.05). No discernable differences in protection were provided by the three compounds. The results indicated that the protective effect is related to the MHb level rather than the specific pretreatment drug.

An Automated Method for the Analysis of Methemoglobin

Production of methemoglobin (met Hb) is effective in treating or preventing cyanide intoxication due to the affinity of cyanide for met Hb. This paper describes an automated method for measuring met Hb in mouse blood utilizing the Roche COB AS FARA centrifugal analyzer and a modified Evelyn–Malloy procedure. Blood samples were spiked with various quantities of potassium ferricyanide to produce met Hb, and automated and manual analyses of these samples were compared. Following validation of the COB AS method, two known met Hb inducers, sodium nitrite and p-aminopropiophenone (PAPP), and two sulfur donor compounds, sodium thiosulfate and ICD #1021, not known to produce met Hb were tested in vivo. Five mice per compound were injected IP and blood samples were analyzed periodically over a time period of approximately 2 h. The automated technique requires only a drop of blood, which allows repeated sampling from the same animal, and can be adapted for blood from different species. A nalyses are rapid and sensitive, and results are reproducible.

Effect of Sulfur Mustard Exposure on Human Epidermal Keratinocyte Viability and Protein Content

Sulfur mustard (HD) is a bifunctional alkylating agent that has mutagenic, cytotoxic, and vesicating properties (1–3). Although HD preferentially alkylates DNA, it is also known to modify RNA and proteins covalently (4). DNA alkylation has been postulated to be the molecular mechanism that initiates a cascade of events terminating in vesication (5). DNA alkylating agents, like HD, have been shown to cause unbalanced cell growth, a condition that occurs when cells exposed to cytotoxic drugs increase in cell volume, protein, and RNA content as cellular mass accumulates, but the cells fail to undergo cell division (6, 7). Depending on concentration, HD will produce different effects in vitro, ranging from inhibition of proliferation with unbalanced cell growth at lower concentrations to cytotoxicity at higher exposure levels (4,8). With an inhibition of proliferation occurring with HD-exposed human epidermal keratinocytes (HEKs), measures of biochemical parameters taken from cultures at extended times postexposure must be standardized to account for differences in cell number. The primary objective of these studies was to assess the feasibility of using protein as a means of standardizing data across HD treatment groups.

Anonlethal, Anesthetized Canine Model for Efficacy Evaluation of Anticyanide Therapy

Efficacy evaluations of anticyanide therapeutic compounds historically have used lethality in unanesthetized animals as the toxic endpoint, and a nonlethal, repeated-testing, anesthetized canine model has been reported. Time to respiratory arrest (TRA) induced by a continuous, slow intravenous (IV) infusion of sodium cyanide (Na CN) was shown to be a consistent, well-defined endpoint in anesthetized canines. Thirty seconds after respiratory arrest (RA), an IV bolus of a methemoglobin-forming compound reversed the respiratory effects. This study was designed to determine the variability in TRA, survivability of anesthetized dogs repeatedly infused with Na CN and treated with hydroxylamine, replicability of the procedure within an animal and between animals, and development of trends in data. Four animals were anesthetized, intubated, catheterized, and instrumented to record respiratory rate and heart rate. Immediately following baseline data collection, a 4-mgl m L. Na CN solution w as infused at a rate of 2 m Llmin. Following a 10-s period without functional respiration, infusion was stopped and this moment was designated as RA. Hydroxylamine therapy was administered 30 s after RA. There were 4 replicate experiments per animal with a 1-week washout period between replicates. Interanimal variability in TRA was significant (p = <.04). The average variability in TRA within an animal was less than 10%. Baseline heart and respiratory rates were not altered significantly. Data confirm, by replicate testing, the utility of this model.

Acetylcholinesterase Inhibition Measurements for the Evaluation of Decontaminant Efficacy Following Percutaneous Organophosphorus Compound Exposure

A rapid and sensitive in vivo method for the evaluation of skin decontaminant efficacy following percutaneous exposure to organophosphonates (OPs) was developed using erythrocyte acetylcholinesterase (AChE; EC 3.1.1.7) inhibition in the rabbit as an end point. The level of AChE inhibition was evaluated for use as a more humane means of assessing skin decontaminant efficacy than lethality-based methods. Groups of anesthetized animals were exposed percutaneously to either of two highly toxic OPs [thickened soman (TGD) or VX], and 2 min later were treated with a known effective skin decontaminant or were untreated (negative control). Blood samples were drawn and assayed for AChE activity 5 min before TGD or VX exposure and at 30, 60, and 120 min after exposure. Percent AChE inhibition relative to preexposure levels was calculated at each postexposure time for each animal in control and treatment groups. Efficacy data based on percent AChE inhibition were compared with results from previous efficacy studies p...