Air Pollution, the Automobile, and Public Health (1988) / Chapter Skim
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Identifying Neurobehavioral Effects of Automotive Emissions and Fuel Components
Identifying Neurobehavioral Effects of Automotive Emissions and Fuel Components
Pages 631-658
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(it) 1988 by the Health Effects Institute.
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tOXlClty. Second, a review is provided of what is currently known about the neurobehavioral toxicity of automotive emissions and fuel constituents.
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Acute performance impairment can increase accident proneness and lower work efficiency; thus there can be serious consequences of even small lapses of coordination, vigilance, or visual sensitivity in operators of all types of transportation machinery. Irritation and sensory effects perhaps the most common complaints elicited by automotive emissionsreduce the perceived quality of life, cause people to change their lifestyles (by allocating their time to less distressful activities)
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Toxicity in Repeated or Continuous Exposures After acute toxicity has been examined, repeated exposure experiments should be undertaken, typically 28- or 90-day subchronic exposures with routine examination of neuropathology, measurement of motor activity (preferably in the home cage) , and routine use of functional observational batteries.
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Quick and simple tests of sensory impairment should be developed that can be used for screening in conjunction with functional observation batteries. At the same time, psychophysical procedures that are more comprehensive should be developed; these should be directed at specific sensory and perceptual impairments, for example impairment of complex auditory and visual discriminations.
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as well as adverse behavioral effects of exposure result in neurochemical changes. It is therefore difficult to interpret the significance of acute neurochemical changes without correlated functional observations.
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, after the identification of neurochemical changes. There probably will not be tests for neurobehavioral toxicity comparable to in vitro tests for mutagenicity (that is, the Ames test)
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During the 1984 Olympics in Los Angeles, concern about the potential effects of automotive emissions and photochemical products on performance and health prompted recommendations for the siting of athletic comnetitions and for traffic control, as well as for training and competition schedules (McCafferty 1981)
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Quantitative procedures should be developed using eyeonly exposures to provide estimates of aversiveness derived from behavior under the control of irritant stimulation, and from measuring blink, heart, and respiratory rates. Behavioral Effects.
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Thus low concentrations of automotive emissions or photochemical reaction products can impair wheel-running performance. The mechanism by which these changes are produced should be a focus of the research agenda because it is of interest per se and because it contributes to risk analysis.
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Several mechanistic experiments indicate that the suppression of wheel running performance was probably not due to acute aversiveness of O3 Wood (1979, 1981a) developed a procedure that permits direct behavioral assessment of the aversive properties of inhaled materials.
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Compared to lever pressing for food, lever pressing for wheel running was much more sensitive; thus the effects of O3 cannot be attributed to an effect on lever-pressing behavior per se. The most important implication of these mechanistic experiments is that O3 at low concentrations reduces the rewarding properties of exercise.
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Repeated exposures should reveal the agents responsible for rebound hyperactivity. Mechanistic studies should focus on behavioral determinants of sensitivity and associated changes in irritant receptors in the upper airways, lung or lung innervation, frank lung injury, and alterations in the peripheral or central nervous systems.
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Carbon Monoxide The neurobehavioral effects of CO have been intensively studied (Laties and Merigan 1979~. Most effects on behavior generated by exposure to low concentrations of
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The time course of respiratory depression was studied during repeated exposure to two concentrations of formaldehyde (1.0 ppm, top left; 3.1 ppm, middle left) or acrolein (0.5 ppm, top right; 1.7 ppm middle right)
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Petroleum Hydrocarbons Aromatic and aliphatic hydrocarbons and alcohols all can produce acute performance impairment; the more volatile and lipophilic the fuel, the more likely that such impairments could result following inhalation. Petroleum hydrocarbons display a variety of effects: some may resemble central nervous system depressants in their ability to increase the frequency of behavior suppressed by punishment, in their anti Although controversy surrounds the studies cited to document the syndrome's existence (Grasso et al.
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Acute effect stud ies would help determine if the prevention of acute effects of petroleum hydrocarbons is sufficient to prevent chronic toxicity. Acute performance impairment should be a major focus of effort.
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The fuel additive tetraethyllead has been responsible for multiple deaths from neurotoxicity and was the focus of a major public health controversy (Rosner and Markowitz 1985~. The neurobehavioral toxicity of Pb would most probably have been detected had some systematic approach to testing been in place.
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Initial screening for subtle sensory or perceptual impairments, affective disorders, or cognitive and intellectual dysfunction needs to be conducted, and, finally, highly focused studies may be needed to fully characterize hazards using methods that are dictated by the nature of the system or function affected, such as specialized evaluations and refined neuropathological, neurochemical, and neurophysiological techn~ques. Since the neurobehavioral toxicity of
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This chapter has described adverse neurobehavioral effects of automotive emissions and offered research recommendations to facilitate their detailed characterization. · Neurobehavioral toxicity has not been evaluated thoroughly for most of the compounds that are known to produce adverse effects, nor have screening and evaluation procedures for such toxicity been applied systematically to the universe of chemicals that mobile sources produce.
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Recommendation 5 Eye irritation is one of the most frequently complained-about effects of automotive emissions and photochemical products. Quantitative procedures should be developed using eye-only ex posures to provide estimates of aversiveness derived from behavior under the control of irritant stimulation, and from measurement of blink, heart, and respiratory rates.
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Recommendation 14 The neurobehavioral toxicity of petroleum hydrocarbons in unleaded automotive fuels has received virtually no serious atten tion. Acute performance impairment should be a major focus of investigation; acute effect determinations are also necessary to ascertain if preventing acute effects will prevent chronic toxicity.
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Recommendation 18 More sensitive animal models of methanol toxicity should be developed, perhaps through the manipulation of folate metabo lism. Repeated or continuous exposure of susceptible individuals to low concentrations of methanol should be undertaken to determine if acidosis can be produced, and if systemic acidosis is a precondi tion for the expression of toxicity.
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L., and Identifying Neurobehavioral Effects Plata, R
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1985b. Recent observations on the neurobehavioral toxicity of carbon disulfide, Neurotoxicology 6:8188.
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1966. Eye irritation response at low concentrations of irritants, Arch.
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1985e. Peripheral nerve function, 40 CFR 798.6850 in Toxic Substances Control Act Test Guidelines; Final Rules, Fed.
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