Toxicological assessment of heat transfer fluids proposed for use in solar energy applications

Abstract

The rapid expansion of solar technology will result in the introduction of new materials into large numbers of residential dwellings. While some of these materials have been evaluated toxicologically for industrial applications, their use in residential solar energy systems require that they be more closely scrutinized for human health hazards. Twenty-one commercial heat transfer fluids which included ethylene and propylene glycol, silicone oils, and various hydrocarbon oil formulations were evaluated for acute oral toxicity in the rat, dermal and ocular irritation in the rabbit, and mutagenic potential in the Salmonella mutagenicity (Ames) test (TA 1538, TA 98, TA 1538, TA 1537, TA 100). Oral, 24-hr LD50 values ranged from 1.9 g/kg for a polyalkylene glycol formulation to > 24 g/kg for most hydrocarbon and silicone oils and propylene glycol-based products. None of the fluids were more than mildly irritating to rabbit skin. One fluid produced reversible corneal damage and transient conjunctivitis was observed in most animals treated with hydrocarbon oil and ethylene glycol formulation. None of the fluids were mutagenic in the Ames test at concentrations ranging from 10 μg to 100 mg per milliliter. These results suggest that most of the fluids may be considered relatively safe for use in residential solar energy applications.