Dermal exposure, organophosphates

Murphy SD. 1980. Toxic interactions with dermal exposure to organophosphate insecticides [Abstract]. Toxicol Lett 5(Supplement 1) 34. 

The NOAEL and LOAEL values for each effect after dermal exposure are shown in Tables 2-7, 2-8, and 2-9 for mineral oil hydraulic fluids, organophosphate ester hydraulic fluids, and polyalphaolefin hydraulic fluids, respectively. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding death in humans after dermal exposure to organophosphate ester hydraulic fluids. 

Several animal studies conducted histological examination of the heart following intermediate-duration dermal exposure to organophosphate ester hydraulic fluids. No cardiovascular effects were observed in rats exposed to 5,750 mg/kg/day of Fyrquel 220 (MacEwen and Vemot 1983), or rabbits exposed to 1,000 mg/kg/day of cyclotriphosphazene (Kinkead et al. 1989c, 1990) or an unspecified amount of Cellulube 220 (Carpenter et al. 1959). 

Two intermediate-duration studies examined hematological parameters (e.g., red blood cell levels, hemoglobin levels) following dermal exposure to organophosphate ester hydraulic fluid. No hematological... 

A study with a dog exposed to an occluded dermal dose of TOCP labeled with radioactive phosphorus provides limited evidence that organophosphate esters in hydraulic fluids may be widely distributed after dermal absorption (Hodge and Sterner 1943). Similar widespread distribution of radioactivity among tissues was observed in male cats after dermal exposure to [uniformly labeled 14C-phenyl]TOCP (Nomeir and Abou-Donia 1986). Tissues and fluids with the highest concentrations of radioactivity in these studies included the bile, gall bladder, urinary bladder, liver, kidney, and fat, thus suggesting that TOCP and metabolites are somewhat preferentially distributed to these tissues. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding excretion in humans after dermal exposure to organophosphate ester hydraulic fluids. However, a human study using the tricresyl phosphate isomer tri-orf/w-cresyl phosphate (TOCP) was located. 

The lack of corroborative case reports, epidemiological data, or animal data (see next paragraph) makes the association between dermal exposure to mineral oil hydraulic fluids and peripheral neuropathy uncertain. Nonetheless, the presence of organophosphate esters, some of which are demonstrated neurotoxic agents, in most mineral oil hydraulic fluids (they often are added as anti-wear agents) suggests that they may play a causative role if such an association exists. 

The range of responses noted for the different fluids, as well as the absence of inhalation or dermal data for many organophosphate hydraulic fluids known to be manufactured, makes it difficult to conclude whether inhalation or dermal exposure to organophosphate fluids, as a class, will produce neurological effects in... 

Polyalphaolefin Hydraulic Fluids. Because no chronic-duration human or animal inhalation, oral, or dermal exposure studies using polyalphaolefin hydraulic fluids were located, chronic-duration inhalation or oral MRLs could not be derived. Systemic toxicity studies in which animals were exposed via inhalation, oral, and dermal routes would be useful in identifying the end points of toxicity for humans living at or near hazardous waste sites and exposed for chronic durations. Further carcinogenicity studies on individual organophosphate ester components of hydraulic fluids maybe useful. 

Organophosphate Ester Hydraulic Fluids. Organophosphate ester hydraulic fluids are used in applications that require a degree of fire resistance such as in aircraft. EPA (1992b) has noted that aircraft mechanics may have dermal exposures of 1,300-3,900 mg/day and that 2,200 aircraft workers are routinely exposed to tributyl phosphate, while another 43,000 mechanics may be exposed at various times. Estimates of worker exposure in other industries were not found in the available literature. General population and military personnel exposure to organophosphate ester hydraulic fluids is likely to be much lower than exposure to mineral oil hydraulic fluids because these fluids have more specialized uses. 

---