Organophosphate additives

A personal sampling method for common organophosphate additives in hydraulic fluids in occupational air was developed with the aim of exposure assessment in working atmospheres potentially contaminated by hydraulic fluids, simultaneously collecting both the aerosols and the vapours. The described sampler combined a glass fibre filter with a Chromosorb 106 adsorbent tube. Desorption was performed with dichloromethane for GC/MS analysis (Solbu et al. 2007). 

Organophosphoms compounds, primarily phosphonic acids, are used as sequestrants, scale inhibitors, deflocculants, or ion-control agents in oil wells, cooling-tower waters, and boiler-feed waters. Organophosphates are also used as plasticizers and flame retardants in plastics and elastomers, which accounted for 22% of PCl consumed. Phosphites, in conjunction with Hquid mixed metals, such as calcium—zinc and barium—cadmium heat stabilizers, function as antioxidants and stabilizer adjutants. In 1992, such phosphoms-based chemicals amounted to slightly more than 6% of all such plastic additives and represented 8500 t of phosphoms. Because PVC production is expected to increase, the use of phosphoms additive should increase 3% aimually through 1999. 

In addition to effects mediated through glucocorticoid secretion (stress-related), a hypothetical mechanism for direct immunotoxicity of organophosphates is the inhibition of esterases and stabilization of the lysosomal membrane of lymphocytes, thus blocking release of lymphokines (Sharma and Reddy 1987). 

A recent method, still in development, for determining total 4-nitrophenol in the urine of persons exposed to methyl parathion is based on solid phase microextraction (SPME) and GC/MS previously, the method has been used in the analysis of food and environmental samples (Guidotti et al. 1999). The method uses a solid phase microextraction fiber, is inserted into the urine sample that has been hydrolyzed with HCl at 50° C prior to mixing with distilled water and NaCl and then stirred (1,000 rpm). The fiber is left in the liquid for 30 minutes until a partitioning equilibrium is achieved, and then placed into the GC injector port to desorb. The method shows promise for use in determining exposures at low doses, as it is very sensitive. There is a need for additional development of this method, as the measurement of acetylcholinesterase, the enzyme inhibited by exposure to organophosphates such as methyl parathion, is not an effective indicator of low-dose exposures. 

Brandt [200] has extracted tri(nonylphenyl) phosphite (TNPP) from a styrene-butadiene polymer using iso-octane. Brown [211] has reported US extraction of acrylic acid monomer from polyacrylates. Ultrasonication was also shown to be a fast and efficient extraction method for organophosphate ester flame retardants and plasticisers [212]. Greenpeace [213] has recently reported the concentration of phthalate esters in 72 toys (mostly made in China) using shaking and sonication extraction methods. Extraction and analytical procedures were carefully quality controlled. QC procedures and acceptance criteria were based on USEPA method 606 for the analysis of phthalates in water samples [214]. Extraction efficiency was tested by spiking blank matrix and by standard addition to phthalate-containing samples. For removal of fatty acids from the surface of EVA pellets a lmin ultrasonic bath treatment in isopropanol is sufficient [215]. It has been noticed that the experimental ultrasonic extraction conditions are often ill defined and do not allow independent verification. 

Organophosphate esters are among the most widely used classes of synthetic compounds in hydraulic fluids. They are used as anti-wear additives in mineral oil hydraulic fluids and are significant components in certain fire-resistant hydraulic fluids (FMC 1991c, 1991d, 1992a, 1992b Wills 1980). 

Additionally, no changes were seen in the type or incidence of developmental anomalies observed in the pups of male and female rats that had been orally exposed to triphenyl phosphate, another component of some organophosphate ester hydraulic fluids at doses <690 mg/kg/day for 91 days, including through mating and gestation (Welsh et al. 1987). 

In addition, organophosphate esters also are used as antiwear additives in hydraulic fluids and other lubricants of the organophosphate esters discussed in this profile, Durad 110, 125, 220B, and 300 are categorized by their manufacturers as antiwear additives and not as hydraulic fluids (FMC 1991c, 1991 d, 1992a, 1992b Marino and Placek 1994). 

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