A short list of the likely pathogens in car exhaust:

• Carbon Monoxide
• Nitrogen dioxide
• Sulphur dioxide
• Suspended particles including PM-10, particles less than 10 microns in size.
• Benzene
• Formaldehyde
• Polycyclic hydrocarbons

Background Information - Adverse Health Effects of Chronic Exposure to Petroleum Combustion Products. On November 18, 1994, the first-ever conference on "Air Pollution: Impacts on Body Organs and Systems" was held in Washington, D.C. by the National Association of Physicians for the Environment. An abridged version follows. The relevance of this perspective increases with increasing air pollution and climate change. 2008 Update.

Jaffe and Badman at the same conference summarized the effects of polluted air :

"Blood perfuses all of the body's organs and can carry toxic substances as well as beneficial substances, such as oxygen, to them. Air pollution is the source of many materials that may enter the human bloodstream through the nose, mouth, skin, and the digestive tract. Chemicals known to be harmful, such as benzene, lead and other heavy metals, carbon monoxide, volatile nitrites, pesticides, and herbicides. These substances have been shown to produce harmful effects on the blood, bone marrow, spleen, and lymph nodes. Blood cells are constantly undergoing turnover, with new blood cells entering the circulation as mature cells are lost, making the blood system especially vulnerable to environmental poisoning. For example, lead interferes with normal red blood cell formation by inhibiting important enzymes. In addition, lead damages red blood cell membranes and interferes with cell metabolism in a way that shortens the survival of each individual cell. Each of these harmful effects can result in clinical anemia.

Benzene and other less known hydrocarbons are produced in petroleum refining, and are widely used as solvents and as materials in the production of various industrial products and pesticides. Benzene also is found in gasoline and in cigarette smoke. It has been shown that exposure to benzene is related to the development of leukemia and lymphoma. Benzene has a suppressive effect on bone marrow and it impairs blood cell maturation and amplification. Benzene exposure may result in a diminished number of blood cells or total bone marrow loss. A number of metabolites appear to be involved in this process, and there may be several targets of toxicity, including stem, progenitor, and some stromal cells.

Common air pollutants also have an affect on blood and thus on organs of the body. For example, carbon monoxide binds to hemoglobin two hundred times more avidly than oxygen and distorts the release to the tissues of any remaining oxygen. Thus, CO poisoning is  a form of suffocation.  Carbon monoxide can exacerbate cardiovascular disease in humans. Some airborne chemicals stimulate the immune system to activate leukocytes and macrophages that can produce tissue damage, especially to the cells that line human blood vessels. The combined effect of these events is to accelerate the changes that eventually lead to hypertension and ischemic heart disease.

Cory-Slechta and Lundberg discussed the adverse effects of pollution on the central nervous system: "The central nervous system (CNS) is the primary target for many serious air pollutants, such as lead, which is a major environmental hazard. Research provided evidence that levels of lead exposure associated with central nervous system effects, particularly as manifest in behavioral changes was lower than previously realized. Blood lead concentrations in children were not considered problematic until they exceeded 30 to 40 micrograms per deciliter ('g/dL); however,  studies demonstrated changes in cognitive function at blood concentrations as low as 10 to 15 'g/dL. While children are more susceptible to lead's CNS effects, adults exhibit similar deficits in learning and memory. Advanced aging  increases vulnerability to the toxic effects of lead. In Germany, a large study documented an age-related decline in bone lead concentrations with advancing age. This effect was more pronounced in women than in men, reflecting post-menopausal processes in women which contribute to bone resorption and the release of lead back into the bloodstream. These results mean that brain lead exposure is actually increased during a period of already heightened susceptibility due to concurrent degeneration of other physiological functions, including both CNS and renal functions.

Although lead is the most studied of hundreds of known or suspected neurotoxic air pollutants, other heavy metals, pesticides, and organic solvents also cause neurobehavioral dysfunction. Expanded research in behavioral neurotoxicology is urgently needed. Changes in mood, cognition, and behavior are endpoints that need to be evaluated in addition to cancer rates or mortality data and may be more common. In various studies, increased levels of air pollutants are accompanied by increased psychiatric emergency calls and hospital admissions, behavior changes, and a lessened sense of well-being. Irritating odors and cigarette smoke have been found to increase aggressive behavior, and to decrease helping behavior and altruism, leading to a degradation of social interaction."

Goldstein and Albright discussed immune system effects: "The effects of airborne pollutants on the immune system have been most widely studied in the respiratory tract. An airborne pollutant may enter the respiratory tract as a volatile gas (e.g., ozone, benzene), as liquid droplets (e.g., sulfuric acid, nitrogen dioxide), or as particulate matter (e.g., components of diesel exhaust, aromatic hydrocarbons). These pollutants interact with the immune system and may cause local and systemic responses ranging from overactive immune responses to immunosuppression. Most airborne pollutants are small molecular weight chemicals that must be coupled with other substances (e.g., proteins or conjugates) before they can be recognized by the immune system and cause an effect. Some disorders which may occur because of pollutants in the respiratory system are the following:

Immunosuppression can be demonstrated following exposure to polycyclic aromatic hydrocarbons (e.g.,tetrachlordibenzo-p-dioxin).

Hypersensitivity reactions (e.g., occupational asthma) can occur following exposure to toluene diisocyanate and other volatile chemicals.

There is clearly an underlying genetic basis for susceptibility to immunologic disease resulting from exposure to pollutants, but knowledge in this area is rudimentary at this time. For example, there is little understanding of genetically-determined susceptibility or resistance to pollutant-induced immune disorders. There is a lack of appropriate in vitro models, and it is difficult to identify specific, biologically-active substances that may be linked to immune disorders."

Workplace Exposure to Vehicle Exhaust and Chronic Illness

Here is a summary of a report on one patient with a known chemical exposure, as an example: Mr. A had been exposed to diesel and gasoline engine exhaust in the workplace from 1982 onward and had become too ill to work by Oct. 1993. Improvements to his work environment were not made until 1992, but apparently these were not adequate and he continued to be ill through 1993. He developed a chronic illness in the mid-80's which was slowly progressive and he beleived that chemical exposure at work had made him ill.

Mr. A manned a parts counter in a vehicle repair shop. The ventilation of this indoor work-space was judged to be inadequate and Mr A was exposed to significant concentrations of exhaust products which include a number of pathogenic possibilities.

His chief complaints were: chronic fatigue, recurrent flu-like illness, limited exertional tolerance, vertigo, dyspepsia with epigastric pain, chest pain with episodes of shortness of breath, cognitive dysfunction, anxiety. He described progressive dysfunction over several years and was concerned that exhaust exposure at work was making him ill. He described a progressive loss of tolerance for physical exertion - attempts at vigorous exertion left him exhausted, weak, and dizzy with cognitive dysfunction; recovery from, for example, attempts to play ice-hockey would often take 48 hour or longer. He had trouble concentrating and suffered recent memory loss. He often felt severe fatigue with difficulty concentrating and memory drop outs at work. He withdrew from work Oct. 1993. He was more attentive to food choices and good nutrition and attempted to follow a graded exercise program. He  reported benefit by staying away from the work environment and controlling his diet.

Prolonged exposure to exhaust gases seem to induce allergy symptoms or hypersensitivity. Activated immune systems tend to start reacting to airborne and food antigens - exposed patients begin reacting to food materials following a typical pattern of chronic illness, and routinely report intolerance to even short exposures of low concentrations of airborne chemicals. Unfortunately there is very little research to help us understand this problem. Since chronic fatigue syndrome has become a common term, studies have been reported showing a scatter of immune and endocrine abnormalities but no simple diagnostic test has emerged. Tests of indoor air quality were conducted but were inadequate to access his exposure.

Index Chemicals  Benzene and the polycyclic hydrocarbons are index chemicals - examples of the many chemicals present in combustion products and while the descriptions of the chemicals are very general, the reader should have no doubt that chronic exposure can produce profound and long-lasting changes in biological function. This information is taken directly from information bulletins issued by the U.S. Agency for Toxic Substances and Disease Registry Division of Toxicology 1600 Clifton Road, E-29Atlanta, Georgia 30333 USA.

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