Fluid availability of sports drinks differing in carbohydrate type and concentration.

Plasma D2O-accumulation profiles (qualitative indices of fluid-absorption rates) were determined in eight subjects after ingestion of 275 mL of five D2O-labeled beverages: a water placebo (W), 6% maltodextrin (6% M), and three solutions containing a 6%, 8%, and 10% glucose-fructose mix (6% GF, 8% GF, and 10% GF). Except for W all beverages contained 20 mmol sodium/L and 3 mmol potassium/L. No differences in plasma D2O accumulation were found. Plasma glucose increased at 20 and 30 min after ingestion of the carbohydrate drinks and returned to baseline (6% GF and 6% M) or below (8% GF and 10% GF) by 60 min. Insulin responded similarly and, except for a slightly lower value at 30 min for 6% GF, no differences were detected. It appears that fluids in drinks containing less than or equal to 8-10% carbohydrate (simple sugars or maltodextrins) are made available for dilution in body fluids at similar rates and should be similar in replenishing body fluids lost in sweat during exercise.

Carbohydrate-electrolyte drinks: effects on endurance cycling in the heat.

On three occasions cyclists completed, as fast as possible, two exercise tasks (T1 and T2) separated by 30 min rest. T1 and T2 were equivalent to the work performed during 2 h cycling at 75% VO2max and 30 min at 75% VO2max, respectively. Every 20 min subjects drank 275 mL of a 6% (MC) or 2.5% (LC) carbohydrate-electrolyte beverage or a water placebo (P). The initial drink during both T1 and the rest period contained 20 g D2O as a marker for entry of ingested fluid into blood. No differences in drink effects were found for heart rate, sweat rate, change in plasma volume, rectal temperature, or D2O accumulation in blood. Blood glucose and respiratory exchange ratios were higher and T2 was performed faster with MC than with P. Ingestion of MC can help maintain blood glucose and enhance performance of prolonged cycling exercise without compromising fluid replenishment.

Occupational disease in the rubber industry.

We have studied mortality patterns in a large cohort of rubber workers. We have examined workers exposed to curing fumes, processing dusts, and industrial talc and have begun to evaluate exposures of these workers in detail. Gastrointestinal (especially stomach) cancer appears in excess in processing workers. Lung cancer is excessive in curing workers. Leukemia is increased generally. All three groups studied for respiratory disease have an increase in disease prevalence which is related to intensity and duration of exposure. Since both an increase in stomach cancer and respiratory disease is seen in processing workers, exposures in this area must be controlled. Since both lung cancer and chronic respiratory disease is excessive in curing rooms, this exposure must be controlled. The leukemia risk is probably related to solvents. Whether this is all explainable by past benzene exposure is unknown. Further studies are planned to refine our knowledge concerning these risks so that occupational disease in the rubber industry can be prevented.

Accumulation of deuterium oxide in body fluids after ingestion of D2O-labeled beverages.

A simple low-cost procedure was developed to compare the temporal profiles of deuterium oxide (D2O) accumulation in body fluids after ingestion of D2O-labeled solutions. D2O concentration was measured in plasma and saliva samples taken at various intervals after ingestion of 20 ml of D2O mixed with five solutions differing in carbohydrate and electrolyte concentrations. An infrared spectrometer was used to measure D2O in purified samples obtained after a 48-h incubation period during which the water (D2O and H2O) in the sample was equilibrated with an equal volume of distilled water in a sealed diffusion dish. The procedure yields 100% recoveries of 60-500 ppm D2O with an average precision of 5%. When compared with values for distilled water, D2O accumulation in serial samples of plasma and saliva was slower for ingested solutions containing 40 and 15% glucose and faster for hypotonic saline and a 6% carbohydrate-electrolyte solution. These differences appear to reflect known differences in gastric emptying and intestinal absorption of these beverages. Therefore this technique may provide a useful index of the rate of water uptake from ingested beverages into the body fluids.

Exercise training alters cardiovascular and hormonal responses to intracranial self-stimulation.

Both reinforcing intracranial self-stimulation (ICSS) and physical exercise result in heightened cardiovascular and endocrine responses. This study compared the cardiovascular and endocrine responses to ICSS in rats after either chronic ICSS or treadmill running. Male rats (n = 35) were implanted with bipolar electrodes aimed at the ventral tegmental area of the brain, and those that performed vigorous lever pressing for ICSS (> 50 presses/min; n = 30) were counter balanced into three groups: chronic ICSS (PRESS), chronic run training (RUN), or sedentary controls (CONT). PRESS, RUN, and CONT rats performed ICSS, ran on a motorized treadmill, or sat quietly in cages for 30 min/day, 5 day/wk, for 12 wk, respectively. All animals then performed 30 min of lever pressing for ICSS and were immediately killed. Oxygen consumption, heart rate, blood pressure, rectal temperature, and plasma norepinephrine, epinephrine, and corticosterone increased (P < 0.05) for all groups during lever pressing. PRESS rats did not differ from CONT rats for any variable studied. However, heart rate was lower and oxygen consumption, norepinephrine, and corticosterone were higher in RUN than in CONT rats. Heart and ventricle weights were higher in PRESS and RUN than in CONT rats; body weights were not different. These data suggest that chronic treadmill running results in adaptations that influence cardiovascular and hormonal responses to ICSS.

Studies of respiratory morbidity in rubber workers. Part IV. Respiratory morbidity in talc workers.

Pulmonary function tests, chest x-rays, and respiratory questionnaires were administered to eighty talc workers and 189 non-exposed rubber workers from three rubber tire manufacturing plants. The talc workers, who were exposed to talc at levels below the current threshold limit value (TLV) of 20 mppcf for nonfibrous talc, had a statistically significantly greater prevalence of productive cough and of positive criteria for chronic obstructive lung disease (COLD) than did the control workers. The talc workers with more than 10 years of exposure had significantly decreased residual FEV 1.0. Multiple regression analysis of FEV 1.0 in the talc workers estimated that each year of exposure to talc dust reduced the FEV 1.0 by 26 ml. Talc workers had a clear increase in respiratory morbidity, despite the absence of chest roentgenographic changes. Based on this study, a safe exposure level for talc appears to be 25 mg/m3 as a time-weighted average.

Simplified description of adsorption breakthrough curves in air cleaning and sampling devices.

Breakthrough curves of organic vapors through a charcoal bed are analyzed by a simplified Theory of Statistical Moments. It is shown that this theory adequately describes the dependence of the shape of the breakthrough curve on concentration of vapor, velocity of air, particle size of charcoal, and length of the bed.

Evaluation of hoods for low volume-high velocity exhaust systems.

Current practice in the design of exhaust hoods for low volume-high velocity exhaust systems is empirical and evaluation of performance is conducted at the completed installation. A procedure is described for laboratory evaluation of prototype hoods using a simulator in conjunction with a tracer aerosol.

Capture efficiency of local exhaust ventilation systems.

A new technique to measure the performance of local exhaust ventilation systems has been developed and tested in both the laboratory and the field. The technique involves the measurement of the capture efficiency of exterior hoods, defined to be the fraction of contaminants given off by a process captured by the exhaust system serving that process. Capture efficiency measurement can be a powerful tool in the evaluation of local exhaust systems, since it is a direct, quantitative measure of system performance; in contrast, indices of performance now in use are either qualitative or measure quantities which may not be related directly to system performance. A basic theory for capture efficiency has been developed, and a prototype system for measuring capture efficiency has been constructed and tested. Preliminary laboratory and field measurements using the system have demonstrated the power of the method, which should find widespread use in the design of new ventilation systems and the evaluation of existing ones.

Air contaminants encountered by firefighters.

The concentrations of eight air contaminants suspected of causing acute and chronic health problems for firefighters were measured in over 200 fires in the City of Boston using a personal air sampler. Threatening concentrations of both carbon monoxide and acrolein were found in a small proportion of the fires. Less hazardous levels of hydrogen chloride, hydrogen cyanide, nitrogen dioxide and carbon dioxide were also noted. Benzene was found in most fires, but at concentrations well below those expected to cause acute injury. The air sampling data have application in treatment of smoke inhalation victims, development of firefighting strategies and selection of respiratory protection devices.

Exposure of firefighters to toxic air contaminants.

A personal sampling apparatus for firefighters was developed to sample the fire atmosphere for CO, CO2, O2, NO2, HCI, HCN and pariculate content. Two fire companies made ninety successful sample runs during structural fires. CO presented a potential acute hazard and particulate concentrations were high. HCN was detected at low levels in half the samples. HCI was detected in only eight samples but on two occasions exceeded 100 ppm. CO2 and NO2 levels and O2 depression do not appear to represent significant hazards.

Health effects of exposure to automobile exhaust--V. exposure of toll booth operators to automobile exhaust.

The exposures of automobile toll booth collectors in the Boston area to selected air contaminants were monitored during the four seasons from 1972 to 1974. The highest carbon monoxide concentrations were found at the in-city toll booths and the highest lead levels at the surburban booths. Biological monitoring for carbon monoxide and lead exposure were closely related to airborne contaminant levels. The study supports the need for environmental control for toll booths located at busy highway and tunnels.

Apparent effect of an azodicarbonamide on the lungs. A preliminary report.

This preliminary study calls attention to the possible pulmonary reactivity of inhaled finely ground azodicarbonamide to which small numbers of workers may be exposed. The conditions in this particular plant involving significant exposure to respirable dust in the mg/m3 range may occur in other plants handling these fine powders. Engineering controls are indicated to protect the workers. We hope that this report will stimulate more detailed studies to validate or refute these observations.

Minimum protection factors for respiratory protective devices for firefighters.

Carbon monoxide and oxygen concentrations were measured in seventy-two structural fires using a personal air sampler carried by working firefighters. In a total sampling time of 1329 minutes the carbon monoxide concentration exceeded 500 ppm approximately 29 percent of the time. The maximum carbon monoxide concentration was 27,000 ppm and in 10 percent of the fires, the maximum concentration exceeded 5500 ppm. Only six runs indicated oxygen concentrations less than 18 percent. On the basis of these exposure data, a minimum protection factor of 100 is proposed for breathing apparatus for structural firefighting.