Synergistic health effects

However, these reactions are also second order in N02 and appear to be too slow at atmospheric NOz levels to be important (Vogt and Finlayson-Pitts, 1994 Peters and Ewing, 1996). There is one aspect of the mechanism that is quite interesting, however, in that the mechanism appears to be at least in part a stepwise process involving the formation of a radical anion intermediate, C1---N02 in the solid, which has been identified by electron paramagnetic resonance (EPR) in both the NaCl and NaBr reactions at room temperature (Wan et al., 1996). This intermediate appears to be remarkably stable and may be responsible for synergistic health effects observed when rats were exposed to a combination of N02 and NaCl aerosols (Last and Warren, 1987). 

The above scientific information on rice bran phytochemicals indicates that a multitude of mechanisms are operating at the cellular level to bring about specific health effects. Several health benefits of rice bran appear to be the result of the synergistic function of the many phytochemicals, antioxidants, vitamins and minerals which operates through a specific immune response. Their role in the biochemical mechanisms at the cellular level which result in major health effects is shown in Fig. 17.1. A short overview summarizing the effect of the various phytochemicals on major health issues such as cancer, immune function, cardiovascular disease, diabetes, altered liver function and gastrointestinal and colon disease will be given below. 

Therefore, it is appropriate and realistic to assume that the greater the number of synthetic chemicals to which a person is exposed, the greater the probability that an individual may experience either a synergistic or an additive health effect. 

Synergism A phenomenon in which exposure to more than one chemical can result in health effects greater than expected when the effects of exposure to each chemical are added together. In simple terms 1 + 1 = 3. If chemicals have synergistic properties, the potential hazards of the chemicals should be reevaluated, considering their synergistic properties. 

BHA has limited cytotoxic effects. When mixed with delta (9)-tetrahydrocannabinol (extracted from marijuana cigarettes), however, synergistic cytotoxicity to lung cells was observed. The study concludes that coexposure to marijuana smoke and BHA can promote deleterious health effects in the lung. I73l... 

Because humans are usually exposed to PAHs in complex mixtures rather than to individual PAHs, it is important to understand the potential interactions between the PAHs and other components of the mixture. Interactions may occur among chemicals in a mixture prior to exposure, or may occur after exposure as a result of differing effects of the mixture components on the body. Synergistic and/or antagonistic interactions with regard to the development of health effects, particularly... 

Using current health effects evaluation procedures, toxicity data for individual congeners may over- or underestimate the actual risk of PCB mixtures because the toxicity of congeners may be influenced by other congeners and chemicals in an additive, more than additive (synergistic), or less than additive... 

Other airborne irritants, as well as ore dust and diesel exhaust, may act synergistically with radon and radon daughters to increase the incidence of adverse health effects. Epidemiological studies report the presence of other airborne irritants in mining environments, including arsenic, hexavalent chromium, nickel, cobalt (Sevc et al. 1984), serpentine (Radford and Renard 1984), iron ore dust (Damber and Larsson 1982 Ediing and Axelson 1983 Radford and Renard 1984), and diesel exhaust (Damber and Larsson 1982 Sevc et al. 1984). 

Karam, P. A., 2003, Health effects of worker and fetal ionizing radiation exposure. Synergist 14(2) 31-34 (February). 

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