Effects of Mixtures

1 IMPROVING ASSESSMENT OF THE RISKS FROM PPCPs IN THE ENVIRONMENT 

When assessing the risk associated with mixtures, oftentimes the data for mixtures are not available. Thus, some scholars have assessed the risk from the individual components and used those to estimate risk using the dose-additivity model (for systemic 

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Fig. 2. Effect of mixture strength on exhaust gas composition (dry basis) and brake specific fuel consumption (BSFC) for an unsupercharged automotive-type engine usiag iadolene fuel, H/C = 1.86, where the ignition is tuned to achieve maximum best torque (MBT), the brake mean effective...

FIG. 13-17 Effect of mixture composition upon K value for n-pentane at 104 C (220 F). K values are shown for various values of VP, weight fraction propane on a methane-free basis for the methane-propane-pentane system. [Hadden, Chem. Eng. Prog. Symp. Sec. 7, 49, 5S (1953).]... 

The presence of several anions in these ionic liquids has the effect of significantly decreasing the melting point. Considering that the formation of eutectic mixtures of molten salts is widely used to obtain lower melting points, it is surprising that little effort has been put into identifying the effects of mixtures of cations or anions on the physical properties of other ionic liquids [17]. 

Lodovici M, Aiolli S, Monserrat C, et al. 1994. Effect of mixture of 15 commonly used pesticides on DNA levels of 8-hydroxy-2-deoxyguanosine and xenobiotic metabolizing enz5mies in rat liver. J Environ Pathol Toxicol and Oncol 13 163-168. 

Effect of mixture components on the viscosity and melting point of the lipstick... 

Application of DSC and HPLC to determine the effects of mixture composition and preparation during the evaluation of niclosamide-excipients compatibility showed that although some reactions occurred, niclosamide was compatible with a majority of common tablet excipients tested [63],... 

Beckles, D.M., C.H. Ward, and J.B. Hughes. 1998. Effect of mixtures of polycyclic aromatic hydrocarbons and sediments on fluoranthene biodegradation patterns. Environ. Toxicol. Chem. 17 1246-1251. 

The effect of mixtures of surfactants and polyelectrolytes on spontaneous, water-catalysed hydrolysis (Fadnavis and Engberts, 1982) was mentioned in Section 4, but mixtures of functionalized polyelectrolytes and cationic surfacants are effective deacylating agents (Visser et al., 1983). Polymerized isocyanides were functionalized with an imidazole group and the deacylation of 2,4-dinitrophenyl acetate in the polyelectrolyte was speeded by addition of single or twin chain quaternary ammonium ion surfactants, up to a plateau value. Anionic surfactants had essentially no effect. It is probable that the cationic surfactants accelerate the reaction by increasing the deprotonation of the imidazole groups. 

This risk assessment is not intended to cover accidents or effects of mixtures. 

The lower explosive limit and minimum explosive concentrations of flax, wool, cotton, jute, hemp and sisal fibres are of the same order of magnitude as those of highly explosive dusts [15], The explosibility of pyrites dusts with sulfur contents above 20% was evaluated experimentally. Dusts of 30% sulfur content gave explosion pressures of 3 bar at pressure rise rates of 16 bar/sec. Mixtures of 60% pyrites and 40% powdered limestone still showed significant pressure effects, and the proportion of limestone actually needed to suppress explosions was considerably above the values currently accepted by mining industries [16], Effects of mixtures of particle sizes in combustible dusts upon minimum ignition temperature (T ") and upon presence or absence of explosion were studied. Presence of 30% of fines in a coarse dust lowers Tf significantly [17], Experimental explosions of polyethylene,... 

Interactions between chemicals administered to humans at high doses have been known for many years in the field of pharmacology. However, these experiences are not directly useful for predicting toxic effects of mixtures of environmental chemicals because the exposure levels for the general human population are relatively low and interactions occurring at high doses may not be representative for low-dose exposures (Konemann and Pieters 1996). 

Chaturvedi et al. (1991) studied the effects of mixtures of parathion, toxaphene, and/or 2,4-D on the hepatic mixed-function oxygenase in ICR male mice. They found that a 7-day toxaphene pretreatment enhanced the hepatic biotransformation of parathion and its metabohte paraoxon, both in the presence and absence of NADP. However, in the absence of NADP the enhancement was minor. The authors suggested that toxaphene induced the metabohc pathways of parathion and paraoxon involving the mixed-function oxygenase and that paraoxonase is not involved in the... 

Chaturvedi (1993) also examined the effect of mixtures of 10 pesticides (alachlor, aldrin, atrazine, 2,4-D, DDT, dieldrin, endosulfan, lindane, parathion, and toxaphene) administered by oral intubations or by drinking water on the xenobiotic-metabolizing enzymes in male mice. He concluded, The pesticide mixtures have the capability to induce the xenobiotic-metabolizing enzymes, which possibly would not have been observed with individual pesticides at the doses and experimental conditions used in the study. ... 

As the temperature of dilute aqueous solutions containing ethoxylated nonionic surfactants is increased, the solutions may turn cloudy at a certain temperature, called the cloud point. At or above the cloud point, the cloudy solution may separate into two isotropic phases, one concentrated in surfactant (coacervate phase) and the other containing a low concentration of surfactant (dilute phase). As an example of the importance of this phenomena, detergency is sometimes optimum just below the cloud point, but a reduction in the washing effect can occur above the cloud point (95). However, the phase separation can improve acidizing operations in oil reservoirs (96) For surfactant mixtures, of particular interest is the effect of mixture composition on the cloud point and the distribution of components between the two phases above the cloud point. 

There are other such scenarios that can be proposed. Evidence exists for both additive and synergistic actions. There is nothing magical about mixtures. The effects of mixtures can be explained in terms of the actions of the individual chemicals, all of which obey the usual physicochemical laws.3°... 

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