Surfactants, exposure effects

There are two additional types of chemical flooding systems that involve surfactants which are briefly mentioned here. One of these systems utilizes surfactant-polymer mixtures. One such study was presented by Osterloh et al. [72] which examined anionic PO/EO surfactant microemulsions containing polyethylene glycol additives adsorbed onto clay. The second type of chemical flood involves the use of sodium bicarbonate. The aim of the research was to demonstrate that the effectiveness of sodium bicarbonate in oil recovery could be enhanced with the addition of surfactant. The surfactant adsorption was conducted in batch studies using kaolinite and Berea sandstone [73]. It was determined that the presence of a low concentration of surfactant was effective in maintaining the alkalinity even after long exposures to reservoir minerals. Also, the presence of the sodium bicarbonate is capable of reducing surfactant adsorption. 

Many bacteria produce surfactants in response to exposure to hydrocarbons, and these have been demonstrated both for those that degrade alkanes and PAHs (Deziel et al. 1996). The positive effect of adding surfactants is, however, equivocal (Deschenes et al. 1996). 

Green FHY, Schurch S, De Sanctis GT, et al. 1991. Effects of hydrogen sulfide exposure on surface properties of lung surfactant. J Appl Physiol 70 1943-1949. 

In summary, intratracheal instillation of CNTs has shown that their potential in eliciting adverse pulmonary effects is influenced by exposure time, CNT dose, CNT biopersistence, surface defects, and metal contamination [71, 72]. Despite the use of surfactants, all studies showed that intratracheal instillation caused major difficulties due to the agglomerative nature of CNTs in a biological environment. More realistic exposure methods, namely inhalation rather than intratracheal administration, are therefore needed for determining the pulmonary toxicity [59, 65, 73]. Several investigations have been performed by using administration different from intra-... 

Frosolono and Currie (1985) investigated the effect of phosgene on the pulmonary surfactant-system (PSS) in groups of six to 14 rats exposed to phosgene at 1 ppm for 4 h. The exposure system and parameters were similar to those described in Section 3.2.1 (Hatch et al. 1986). The actual chamber concentration was 1.0 0.06 ppm. Animals were sacrificed immediately after exposure, or on postexposure days 1, 2, or 3. Pulmonary edema was present immediately after exposure and persisted through day 3. Phosphatidylinositol levels were significantly (p<0.05) decreased compared with controls immediately after exposure only. Phosphatidylserine and phosphatidylethanolamine levels were significantly increased compared with controls on days 1, 2, and 3 postexposure. Phosphatidylcholine levels were increased at all time points compared with controls. 

For topical exposures, determining absorption (into the skin and into the systemic circulation) requires a different set of techniques. For determining how much material is left, skin washing is required. There are two components to skin washing in the recovery of chemicals. The first component is the physical rubbing and removal from the skin surface. The second component is the surfactant action of soap and water. However, the addition of soap effects the partitioning. Some compounds may require multiple successive washing with soap and water applications for removal from skin. 

Bioconcentration may occur as a result of continuous exposure to a certain compound, even at concentrations sufficiently low for no toxic effect to be observed. This process is very relevant in the case of surfactants, due with their affinity for interfaces, since they tend to associate with biological membranes (i.e. the interfaces between organisms and their medium). 

Respiratory effects are more likely to occur after inhalation exposure to high concentrations of chloroform. It has been demonstrated that chloroform has a destructive influence on the pulmonary surfactant (Enhoming et al. 1986). This effect is probably due to the solubility of phospholipids in the surfactant monolayer and can cause collapse of the respiratory bronchiole due to the sudden increase in inhalation tension. Immediate death after chloroform inhalation may be due principally to this effect in the lungs (Fagan et al. 1977). It is unlikely that exposure levels of chloroform in the general environment or at hazardous waste sites would be high enough to cause these severe respiratory effects. 

Curstedt T, Hafinan M, Robertson B, et al. 1983. Rabbit lung after long-term exposure to low nickel dust combustion. I. Effects on phospholipid concentration and surfactant activity. Environ Res 30 89-94. 

Risk assessments for anionic surfactants are obtained by comparing environmental exposure concentrations to effect levels (the quotient method). A protection factor that reflects the environmental safety of the material is calculated by dividing the exposure level by the effect concentration. If the protection factor is greater than 1, the material is deemed safe. Although this approach to assessing risk yields a numerical value that could be interpreted as the relative safety of a compound, comparisons of protection factors for different compounds should be avoided. The risk assessment for each material must be considered separately because of differences in chemical properties and differences in the database used to obtain the protection factor. In addition, the degree of uncertainty in the exposure and effect... 

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