Nutritional influences on the toxicity of environmental pollutants: a review

Environmental Pollutants and Oxidative Stress in Terrestrial and Aquatic Organisms: Examination of the Total Picture and Implications for Human Health

There is current great international concern about the contribution of environmental pollution to the global burden of disease particularly in the developing, low- and medium-income countries. Industrial activities, urbanization, developmental projects as well as various increased anthropogenic activities involving the improper generation, management and disposal of pollutants have rendered today's environment highly polluted with various pollutants. These pollutants include toxic metals (lead, cadmium, mercury, arsenic), polycyclic aromatic hydrocarbons, polychlorinated biphenyls, pesticides and diesel exhaust particles most of which appear to be ubiquitous as well as have long-term environmental persistence with a wide range of toxicities such as oxidative stress among others. Oxidative stress, which may arise from increased production of damaging free radicals emanating from increased pollutant burden and depressed bioavailability of antioxidant defenses causes altered biochemical and physiological mechanisms and has been implicated in all known human pathologies most of which are chronic. Oxidative stress also affects both flora and fauna and plants are very important components of the terrestrial environment and significant contributors of nutrients for both man and animals. It is also remarkable that the aquatic environment in which sea animals and creatures are resident is also highly polluted, leading to aquatic stress that may affect the survival of the aquatic animals, sharing in the oxidative stress. These altered terrestrial and aquatic environments have an overarching effect on human health. Antioxidants neutralize the damaging free radicals thus, they play important protective roles in the onset, progression and severity of the unmitigated generation of pollutants that ultimately manifest as oxidative stress. Consequently, human health as well as that of aquatic and terrestrial organisms may be protected from environmental pollution by mitigating oxidative stress and employing the principles of nutritional medicine, essentially based on antioxidants derived mainly from plants, which serve as the panacea of the vicious state of environmental pollutants consequently, the health of the population. Understanding the total picture of oxidative stress and integrating the terrestrial and aquatic effects of environmental pollutants are central to sustainable health of the population and appear to require multi-sectoral collaborations from diverse disciplinary perspectives; basically the environmental, agricultural and health sectors.

A Common Insecticide Induced-Oxidative Stress in Wistar Rats: Significance for Humans and Implications for Nutritional Modulation of Insecticide Toxicity

OBJECTIVE

This study examined the levels of selected micronutrients and associated biochemical changes in rats exposed to Baygon® insecticide. Arsenic is a toxic metalloid commonly used in insecticides manufacture but unheralded.

METHODS

Fifteen rats, divided into three equal groups: Group I (control); group II (administered 2.5 mg/kg sodium arsenite (SA) on alternate days for four weeks); group III (exposed to 14.0 mL Baygon^® m^-3 cage volume daily for four weeks). Serum levels of arsenic (As), selenium (Se) and zinc (Zn) were determined using flame atomic absorption spectrophotometry (FAAS). Reduced glutathione (GSH), glutathione peroxidase (GPx), and total protein (TP) were determined spectrophotometrically.

RESULTS

Arsenic and Se levels were significantly raised in groups II and III compared with control (p < 0.05), unlike Zn levels that were significantly decreased in groups II and III (p < 0.05) in both. No significant change in the activity of GPx; though the activity increased in the group treated with SA, but decreased in the group treated with Baygon^® compared to control (P < 0.05). Histology of the liver and lung was unaltered in control, but in contrast, the SA-treated group demonstrated moderate fibrous hyperplasia with prominent highly infiltrated portal area in the liver; while the lung revealed thickened alveolar walls from proliferated pneumocytes. In the Baygon^®-treated group, there was mild hyperplasia of the fibrous connective tissue and congested prominent portal areas; while the lung exhibited severe thickened alveolar walls due to proliferated pneumocytes.

CONCLUSION

Exposure of rats to Baygon^® elicited alteration of key trace elements involved in the antioxidant system, culminating in oxidative stress with attendant deleterious effects. One significance of this for humans is that it has great potentials for possible nutritional modulation of insecticide toxicity with micronutrients, especially with zinc, holding great promise in tropical developing countries.

Nutritional Implications of Dietary Interactions: A Review

A large number of dietary interactions have been described. Of these, only a relatively small number have been proved of relevance for human nutrition under the conditions of real diets. These interactions most often occur at the intestinal lumen, but they may also take place during utilization or storage of nutrients. Traditional diets of developing countries, which usually include non-refined cereals and other sources of fibre, may inhibit the bioavailability of mineral nutrients, contributing to specific deficiencies. Drug-nutrient interactions may also impact on nutritional status, particularly in population groups such as the elderly, who frequently receive prolonged medication and may have an inadequate food intake.

Diet composition modifies the toxicity of repeated soman exposure in rats

It was previously demonstrated that diet potently modulates the toxic effects of an acute lethal dose of the nerve agent soman. The current investigation was undertaken to examine the influence of diet on the cumulative toxicity of repeated soman administration. Rats were fed one of four distinct diets (standard, choline-enriched, glucose-enriched, or ketogenic) for four weeks prior to and throughout a repeated soman dosing and recovery regimen. Each diet group included animals exposed to an equivalent volume of saline that served as negative controls. In exposure Week 1, animals received three consecutive daily doses of 0.4 LD(50) soman. In exposure Week 2, animals received four consecutive daily doses of 0.5 LD(50) soman. In exposure Week 3, animals received five consecutive daily doses of 0.5 LD(50) soman. Week 4 constituted a post-exposure recovery evaluation. Throughout the experiment, behavioral function was assessed by a discriminated avoidance test that required intact sensory and motor function. Survival and body weight changes were recorded daily. Differences in toxicity as a function of diet composition became apparent during the first week. Specifically, rats fed the glucose-enriched diet showed pronounced intoxication during Week 1, resulting in imperfect survival, weight loss, and deteriorated avoidance performance relative to all other groups. All rats fed the glucose-enriched diet died by the end of exposure Week 2. In contrast, only 10% of animals fed the standard diet died by the end of Week 2. Also in Week 2, weight loss and disrupted avoidance performance were apparent for all groups except for those fed the ketogenic diet. This differential effect of diet composition became even more striking in Week 3 when survival in the standard and choline diet groups approximated 50%, whereas survival equaled 90% in the ketogenic diet group. Avoidance performance and weight loss measures corroborated the differential toxicity observed across diet groups. Upon cessation of soman exposure during the final week, recovery of weight and avoidance performance in survivors was comparable across diet groups. These results systematically replicate previous findings demonstrating that diet composition exacerbates or attenuates toxicity in rodents exposed acutely to organophosphorus compounds.

Diet composition exacerbates or attenuates soman toxicity in rats: implied metabolic control of nerve agent toxicity

To evaluate the role of diet composition on nerve agent toxicity, rats were fed four distinct diets ad libitum for 28 d prior to challenge with 110 μg/kg (1.0 LD(50), sc) soman. The four diets used were a standard rodent diet, a choline-enriched diet, a glucose-enriched diet, and a ketogenic diet. Body weight was recorded throughout the study. Toxic signs and survival were evaluated at key times for up to 72 h following soman exposure. Additionally, acquisition of discriminated shuttlebox avoidance performance was characterized beginning 24h after soman challenge and across the next 8 d (six behavioral sessions). Prior to exposure, body weight was highest in the standard diet group and lowest in the ketogenic diet group. Upon exposure, differences in soman toxicity as a function of diet became apparent within the first hour, with mortality in the glucose-enriched diet group reaching 80% and exceeding all other groups (in which mortality ranged from 0 to 6%). At 72 h after exposure, mortality was 100% in the glucose-enriched diet group, and survival approximated 50% in the standard and choline-enriched diet groups, but equaled 87% in the ketogenic diet group. Body weight loss was significantly reduced in the ketogenic and choline-enriched diet groups, relative to the standard diet group. At 1 and 4h after exposure, rats in the ketogenic diet group had significantly lower toxic sign scores than all other groups. The ketogenic diet group performed significantly better than the standard diet group on two measures of active avoidance performance. The exacerbated soman toxicity observed in the glucose-enriched diet group coupled with the attenuated soman toxicity observed in the ketogenic diet group implicates glucose availability in the toxic effects of soman. This increased glucose availability may enhance acetylcholine synthesis and/or utilization, thereby exacerbating peripheral and central soman toxicity.

Decreased thiamine and magnesium levels in the potentiation of the neurotoxicity of lead in occupational lead exposure

The relationship between blood lead (Pb) and serum levels of calcium and of neural nutrients such as thiamine and magnesium (Mg) has been determined in a Nigerian population that is occupationally exposed to Pb. Forty-seven male Pb workers were recruited as test subjects and 25 males unexposed to Pb served as controls. The test subjects were classified into three groups, based on severity of exposure to Pb. Blood lead (BPb) and the serum levels of Mg, thiamine, and calcium were determined in both test subjects and controls. The mean blood Pb level was not significantly higher in Pb workers. In contrast, Mg and thiamine levels were significantly decreased (p<0.05; p<0.01, respectively). However, the calcium level was not significantly lower in test subjects than in controls. Also, there was a significant negative correlation between serum thiamine and blood Pb levels (r=-0.50; p<0.01). Furthermore, there was a significant negative correlation between serum calcium and BPb levels (r=-0.41; p<0.01). This study has shown that relatively low BPb levels can enhance Pb absorption and also potentiate Pb neurotoxicity in the presence of decreased serum thiamine and Mg levels.

Toxicity of environmental lead and the influence of intestinal absorption in children

Exposure to metals, particularly lead, remains a widespread issue that is associated with historical and current industrial practices. Whereas the toxic properties of metals are well described, exposure to metals per se is only one of many factors contributing to elevated blood metal concentrations and their consequent health effects in humans. The absorbed dose of metal is affected by geochemical, biochemical, and physiological parameters that influence the rate and extent of absorption. In children, the interplay among these factors can be of critical importance, especially when biochemical and physiological processes might not have matured to their normal adult status. Such immaturity represents an elevated risk to metal-exposed children because they might be more susceptible to enhanced absorption, especially via the oral route. This review brings together the more recent findings on the physiological mechanisms of metal absorption, especially lead, and examines several models that can be useful in assessing the potential for metal uptake in children.

Cadmium and vanadate oligomers effects on methaemoglobin reductase activity from Lusitanian toadfish: in vivo and in vitro studies

Cadmium and two vanadate solutions as 'metavanadate' (containing ortho and metavanadate species) and 'decavanadate' (containing decameric species) (5 mM) were injected intraperitoneously in Halobatrachus didactylus (Lusitanian toadfish), in order to evaluate the effects of cadmium and oligomeric vanadate species on methaemoglobin reductase activity from fish red blood cells. Following short-term exposure (1 and 7 days), different changes were observed on enzyme activity. After 7 days of exposure, 'metavanadate' increased methaemoglobin reductase activity by 67% (P < 0.05), whereas, minor effects were observed on enzymatic activity upon cadmium and 'decavanadate' administration. However, in vitro studies indicate that decameric vanadate, in concentrations as low as 50 microM, besides strongly inhibiting methaemoglobin reductase activity, promotes haemoglobin oxidation to methaemoglobin. Although decameric vanadate species showed to be unstable in the different media used in this work, the rate of decameric vanadate deoligomerization is in general slow enough, making it possible to study its effects. It is concluded that the increase in H. didactylus methaemoglobin reductase activity is more pronounced upon exposition to 'metavanadate' than to cadmium and decameric species. Moreover, only decameric vanadate species promoted haemoglobin oxidation, suggesting that vanadate speciation is important to evaluate in vivo and in vitro effects on methaemoglobin reductase activity.

Incinerator toxic emissions: a brief summary of human health effects with a note on regulatory control

Toxic emissions from municipal solid waste (MSW) and hazardous waste incineration are discussed, with reference to recent reviews and to government standards and controls. Studies of known effects of aromatic hydrocarbons, other organics, dioxins, metals, and gases, on fish, soils, plants, and particularly humans are briefly reviewed. A summary of potential problems with existing and proposed incineration is developed, including: (1) lack of toxicity data on unidentified organic emissions; (2) unavoidability of hazardous metal emissions as particles and volatiles; (3) inefficient stack operation resulting in unknown amounts of increased emissions; (4) formation in the stack of highly toxic dioxins and furans, especially under inefficient conditions, and their build-up in the environment and in human tissue; (5) the lack of adequate disposal techniques for incinerator fly ash and wash-water; (6) the contribution of emitted gases such as NO2, SO2 and HCL to smog, acid rain, and the formation of ozone, and the deleterious effects of these on human respiratory systems; (7) the effects and build-up in human tissue of other emitted organics such as benzene, toluene, polychlorinated biphenyls (PCBs), alkanes, alcohols, and phenols; (8) lack of pollution-control and real-time efficiency-monitoring equipment in existing installations. The inability of regulatory bodies historically to ensure compliance with emission standards is discussed, and a concluding opinion is offered that it is inadvisable to engage in new incinerator construction with present knowledge and conditions.

Effects of micronutrients on metal toxicity

There is growing evidence that micronutrient intake has a significant effect on the toxicity and carcinogenesis caused by various chemicals. This paper examines the effect of micronutrient status on the toxicity of four nonessential metals: cadmium, lead, mercury, and arsenic. Unfortunately, few studies have directly examined the effect of dietary deficiency or supplementation on metal toxicity. More commonly, the effect of dietary alteration must be deduced from the results of mechanistic studies. We have chosen to separate the effect of micronutrients on toxic metals into three classes: interaction between essential micronutrients and toxic metals during uptake, binding, and excretion; influence of micronutrients on the metabolism of toxic metals; and effect of micronutrients on secondary toxic effects of metals. Based on data from mechanistic studies, the ability of micronutrients to modulate the toxicity of metals is indisputable. Micronutrients interact with toxic metals at several points in the body: absorption and excretion of toxic metals; transport of metals in the body; binding to target proteins; metabolism and sequestration of toxic metals; and finally, in secondary mechanisms of toxicity such as oxidative stress. Therefore, people eating a diet deficient in micronutrients will be predisposed to toxicity from nonessential metals.

Modulation of toxicity by dietary and environmental factors

Both epidemiological and experimental evidence indicate that environmental factors may modulate chemical toxicity. Of these, dietary factors have been most thoroughly studied and shown to modulate a number of toxic processes including carcinogenesis. Total energy intake and specific nutrients (protein and specific amino acids, vitamins, and minerals) have been shown to be active in this regard as have a number of non-nutritive dietary factors, most notably phenolic and sulphur-containing compounds, and indoles. The mechanisms by which dietary factors might influence toxicity include effects on bioavailability, phase I or phase II metabolism, scavenging of reactive metabolites, induction of DNA repair processes, inhibition of cell proliferation, induction of differentiation or apoptosis and effects on the immune system. These factors are discussed with emphasis on dietary exposure to modulating factors.

Effect of dietary casein levels on activation of promutagens in the spiral Salmonella mutagenicity assay. II. Studies with induced rat liver S9

In the previous study (Mutation Res., this issue), we showed that increased levels of dietary casein as the sole protein source for male F344 rats decreased the ability of the uninduced liver S9s to activate 2-aminoanthracene (2AN) to a mutagen in strain TA98 using the spiral Salmonella mutagenicity assay. No effects of dietary casein levels were noted for the ability of uninduced liver S9s to activate the promutagens aflatoxin B1 (AFB) and benzo[a]pyrene (BAP). In the present study, we have extended this study to include liver S9s induced with either Aroclor 1254, phenobarbital or 3-methylcholanthrene (3MC). S9s were derived from individual male F344 rats fed for 6 weeks on semisynthetic diets containing 8%, 12% or 22% methionine-supplemented casein as the sole source of protein (diets were made isocaloric by adjusting the corn starch content). Rats were housed in large, raised-bed cages by groups of three/diet/inducing agent. S9 activation mixtures were prepared at 5 mg of S9 protein/ml of S9 mix. Slopes from the linear portions of the mutagenicity dose-response curves were analyzed by ANOVA comparisons. Assays used to elucidate the phase I activities of microsomal preparations were cytochrome P-450 content, cytochrome-c reductase activity, flavin-containing monooxygenase activity, 7-ethoxyresorufin O-deethylation (EROD) activity, N-demethylation of benzphetamine, and para-nitrophenol O-deethylation. Phase II activities were assayed by estimating glutathione (GSH) content and measuring the metabolism of 1-chloro-2,4-dinitrobenzene (CDNB) by glutathione S-transferase in cytosolic preparations. None of the phase I or phase II endpoints were significantly affected by dietary casein levels. In general, increasing levels of dietary casein resulted in increased body and liver wet weight and amount of S9 protein. Aroclor-induced S9s from rats fed the 22% or 12% casein diet were most effective at activating AFB, depending on the lot of Aroclor used for induction; these divergent results were replicated with two groups of rats for each lot of Aroclor. The observed differences between Aroclor lots are assumed to arise from variation in the mix of PCB isomers. The Aroclor-induced S9s did not exhibit any casein-related effects for the activation of BAP or 2AN. For 3MC-induced S9s, the 12% casein diets produced S9s with the highest ability to activate AFB and BAP when standardized for protein content. Phenobarbital-induced S9s did not demonstrate any dietary casein-related effects on the activation of the three model promutagens. These results illustrate the complex interaction between dietary levels of casein, enzyme inducing agent and promutagen.

Effect of dietary casein levels on activation of promutagens in the spiral Salmonella mutagenicity assay. I. Studies with noninduced rat liver S9

Xenobiotic metabolism can be influenced by various nutritional factors, including protein. In the present study, we have examined the effect of dietary protein (casein) levels on the ability of rat liver S9 to activate the promutagens aflatoxin B1 (AFB), 2-aminoanthracene (2AN) and benzo[a]pyrene (BAP) in strain TA98 using the spiral Salmonella mutagenicity assay. S9s were derived from individual male F344 rats fed for 6 weeks on semisynthetic diets containing 8%, 12% or 22% methionine-supplemented casein as the sole source of protein (diets were made isocaloric by adjusting the corn starch content). Rats were housed in large, raised-bed cages by groups of three per diet. S9 activation mixtures were prepared at 5 mg of S9 protein/ml of S9 mix. Slopes from the linear portions of the mutagenicity dose-response curves were analyzed by ANOVA comparisons. Assays used to elucidate the phase I activities of microsomal preparations were cytochrome P450 content, cytochrome-c reductase activity, flavin-containing monooxygenase activity, 7-ethoxyresorufin O-deethylation (EROD) activity, N-demethylation of benzphetamine and para-nitrophenol O-deethylation. Phase II activities in cytosolic preparations were assayed by estimation of glutathione (GSH) content and glutathione S-transferase activity through metabolism of 1-chloro-2,4-dinitrobenzene (CDNB). Increased levels of dietary casein increased liver wet weights and decreased the ability of the S9 to activate 2AN. Dietary casein levels did not influence the S9-mediated activation of BAP; and consistent but nonsignificant increases in activation of AFB were produced by S9 from animals fed the 22% casein diet. The phase I and phase II activities measured here were not altered significantly by dietary casein levels; thus, other, more specific enzymatic activities may account for the mutagenesis data. These results illustrate the complex interaction between dietary levels of casein and promutagen activation mechanisms, which prevents drawing broad generalizations regarding the influence of dietary casein levels on the capacity of hepatic S9s to activate promutagens.

Ozone-induced tissue injury and changes in antioxidant homeostasis in normal and ascorbate-deficient guinea pigs

It has been reported previously that ozone (O3) toxicity from acute (4 hr) exposure is enhanced by ascorbate (AH2) deficiency in guinea pigs. We hypothesized that lung injury from continuous 1-week O3 exposure would also be increased under conditions of AH2 deficiency because of (1) a diminished antioxidant pool to counteract the oxidant challenge, (2) impaired reparation of tissue injury, and/or (3) altered antioxidant redox homeostasis. Female Hartley guinea pigs (260-330 g) were made AH2 deficient by providing a diet similar to guinea pig chow, but having no AH2. The dietary regimen was started 1 week prior to exposure and was continued during exposure to O3 (0, 0.2, 0.4, or 0.8 ppm, 23 hr/day, 7 days) as well as 1 week post-exposure. Bronchoalveolar lavage (BAL) and tissue AH2 were measured in subgroups at the beginning of exposure (1 week on the AH2-deficient diet), at its termination and 1 week post-exposure. AH2 measured in ear tissue punches proved to be an easy and effective monitor for AH2 deficiency. One week on the AH2-deficient diet caused a 70-80% drop in ear, lung and liver AH2, while AH2 in BAL was decreased by 90%. Immediately after the exposure, total BAL protein and albumin (markers of lung permeability) were increased (approximately 50%) at 0.8 ppm with no difference between the dietary groups. O3 caused an increase in total BAL cells and neutrophils in a concentration-dependent manner with only a slight augmentation due to diet. Exposure to O3 caused an increase in lung and BAL AH2 in normal guinea pigs. Glutathione and uric acid were also increased in the lung and BAL after O3 exposure (40-570%) in both dietary groups, and the levels remained elevated during the recovery period. Lung alpha-tocopherol was not changed due to O3. A significant overall diet-related decrease was seen in AH2-deficient guinea pigs, immediately after the exposure and recovery. In summary, lung injury/inflammation following 1 week O3 exposure and recovery were minimally affected by AH2 deficiency. Antioxidants also appeared to increase in response to O3 exposure despite the deficiency in AH2.

Influence of dietary protein concentration on severity of nephropathy in Fischer-344 (F-344/N) rats

Nephropathy is an age-related spontaneous disease of most rat strains, and protein content of diet may affect the severity. The purpose of this study was to determine the effect of a 15% protein nonpurified diet on body weight and severity of nephropathy in comparison to a 23% protein NIH-07 diet. Groups of 25 male and 25 female Fischer-344 (F-344) rats, 6 wk of age, were fed the 23 or 15% protein diet ad libitum for 2 yr. Rats were weighed at 1-4-wk intervals, and mean body weights were determined. Water consumption measurements and urinalysis were done at approximately 3-mo intervals during the second year of the study. At the end of the 2-yr study, kidneys from all rats, including those that died or were euthanatized after the eightieth week of the study, were examined by light microscopy and graded for severity of nephropathy as grades 1-4 (minimal, mild, moderate, marked). Growth patterns and the maximum body weights attained by each sex fed the 23 or 15% protein diet were not significantly different. The severity of nephropathy in male rats was significantly higher when fed the 23% protein diet (2.8 moderate to marked) compared to the 15% protein diet (1.3 minimal to mild). The severity of nephropathy in female rats increased slightly when fed the 23% protein diet (1.5 minimal to mild) compared to the 15% protein diet (1.0 minimal).(ABSTRACT TRUNCATED AT 250 WORDS)

Haematological effects of vanadium on living organisms

Although vanadium has been of great interest for many researchers over a number of years, its biochemical and physiological role is not yet fully clear. There are many papers describing the haematological consequences of its excess in living organisms and most of their data are quoted in this mini-review. The authors of these papers used various laboratory animals, different vanadium compounds, frequently different routes of administration and duration of intoxication. Hence a checklist and comparison of the results are rather difficult. Vanadium reduces the deformability of erythrocytes, and such cells are rather frequently retained in the reticuloendothelial system of the spleen and eliminated faster from the blood stream (Kogawa et al., 1976). Vanadium produces peroxidative changes in the erythrocyte membrane, this leading to haemolysis. Therefore, the depressed erythrocyte count in animals intoxicated with vanadium may be the consequence of both the haemolytic action of vanadium and the shortened time of survival of erythrocytes. Changes of the haem precursor level in blood serum and urine observed in humans exposed occupationally to vanadium suggest an influence of this element on haem synthesis. This problem requires, however, further studies and observations. Changes occurring under the influence of vanadium on the leukocyte system of animals suggest the influence of this element on the resistance of the organism, but the mechanism of the action of vanadium still requires elucidation.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of agricultural pesticides on humans, animals, and higher plants in developing countries

Undesirable side effects that result from the indiscriminate use of agricultural pesticides in developing countries are widespread. This has captured the attention of health workers, governments, and environmental protection agencies. In fact, the potential health effects of long-term exposure to humans, animals, and higher plants are of great concern. This study examines the effects of agricultural pesticides on such living forms and explores modes of action, and presents strategies to minimize the deleterious effects of pesticides to living forms in developing countries.

Refugee income generating projects and occupational health

The shift from purely emergency relief for refugees in developing countries to aid within the context of development strategies is slowly gathering momentum (UN, 1983; UNHCR, 1984; Simmonds, 1984). Such a move implies that if self-reliance is to be a realistic goal then employment for refugees is essential; a number of income-generating schemes are therefore being both proposed and developed (ILO, 1983 and 1984). Many of these schemes have implications for the health of the refugees, so this paper summarises some occupational health hazards and offers suggestions for future action.

Effect of ozone on serum lipids and lipoproteins in the rat

Exposure of male rats to 0 (air), 1, 1.75, and 3 ppm ozone (O3) 5 hr/day for a total of 10 days resulted in a positive linear relationship between ozone concentration and the concentrations of serum total lipoprotein free cholesterol (FCh) and high-density lipoprotein total cholesterol (HDL-Ch). The latter response was reflected in both its free (HDL-FCh) and esterified (HDL-ChE) components. On the other hand, serum triglycerides (TG) showed a marked decreasing linear trend with increasing ozone concentration. As judged by decreased body weights with no accompanying differences in feed consumption, apparent metabolic rate increased as ozone concentration increased. In another experiment, male rats were exposed 5 hr/day to either air or 1 ppm O3 for a total of 15 days. Groups of animals from each exposure were sampled at times ranging from immediately after to 44 hr postexposure. In agreement with the concentration response study, effects of O3 included increases in serum total cholesterol (Ch), HDL-Ch and HDL-FCh, and a decrease in TG. In addition, the degree of effects appeared to be maintained over the 44-hr period and to be greater than that observed at 1 ppm O3 in the concentration-response study.

Modulation of nitrogen dioxide toxicity by lithium

The effect of short-term intake of LiCl in drinking fluid on NO2 toxicity was studied in mice as a function of mortality and of specific activities of mouse liver alcohol dehydrogenase (L-ADH) and aldehyde dehydrogenases (L-ALDH). Pretreatment with LiCl for 10 days decreased mortality in mice exposed to 60 to 70 PPM NO2 for 6 hr compared to controls. Pretreatment with LiCl for 10 days under continued exposure to 5 PPM NO2 resulted in a decrease in liver weight compared to control. Lithium treated mice exposed to NO2 showed less gain in body weight than the controls treated with LiCl and exposed to air. The latter group showed an induction of mitochondrial but not cytoplasmic L-ALDH and the NO2 exposure did not alter endogenous L-ALDH from corresponding controls. This induction of mitochondrial ALDH was associated with an increase in both Vmax and the apparent Km. Exposure to NO2 for 10 consecutive days resulted in inhibition of cytoplasmic L-ALDH. The data suggest that Li+ antagonized NO2 toxicity. A possible mechanism for reduction of NO2 toxicity by LiCl may be due to Li+ action on stabilizing cell membranes and/or modifying intercellular pulmonary response to NO2 injury.

Minireview: the health implications of water treatment with ozone

Ozone is a highly efficient disinfectant which may have significant advantages in water treatment compared to chlorine. It has, however, been shown that mutagenic and possibly carcinogenic byproducts may be produced under certain conditions of ozonation. Light chlorination following ozonization may meet the highest standards of disinfection. In addition the destruction of much of the organic matter by prior ozone treatment may well result in less harmful chlorinated and brominated products in the finished water. In many cases ozone treatment alone may suffice. It would be desirable to test with long term in vivo experiments which of the alternatives produces the best combination of microbiologically clean and pleasant water with minimum mutagenic and carcinogenic effect.

Vitamin E supplementation and respiratory effects of ozone in humans

To determine whether vitamin E (di-alpha-tocopherol) supplementation could protect against short-term respiratory responses to O3 exposure its effects were investigated in young healthy adult volunteers. Experimental groups received 800 or 1600 IU vitamin E per day for 9 or more wk, while control groups received placebo. Subjects were then exposed for 2-h periods to 0.5 ppm O3, with secondary stresses of heat and intermittent light exercise. Responses to O3 exposure, evaluated in terms of symptoms, forced expiratory performance, and single-breath nitrogen washout, were not significantly different between vitamin E and placebo groups.

Effects of ozone exposure in Canadians and Southern Californians. Evidence for adaptation?

Comparison of published reports on physiological effects of exposure to ozone (O3) suggests that Canadians are more reactive than southern Californians. Responses of subjects and experimental methods were compared in a cooperative investigation of this apparent difference in reactivity. Four Canadians and four Californians were exposed to 0.37 ppm O3 in purified air at 21 degrees C and 50% relative humidity for 2 hours with intermittent light exercise. Exposures to purified air alone served as controls. Responses of subjects were similar to those observed previously: Canadians on the average showed greater clinical and physiological reactivity to exposure than did Californians, who were no more than minimally reactive. Canadians also showed larger increases in erythrocyte fragility following exposure. No methodological differences sufficient to explain different results of previous studies were found. Although other possible explanations have not been ruled out entirely, adaptation of southern Californians to chronic ambient O3 exposure is a rational hypothesis to explain these results.