Toxicity of Sodium Chloride to House Sparrows (Passer Domesticus)

Abstract

Sodium chloride (NaCl) is widely used as a deicing agent on roadways. There are numerous anecdotal reports of poisoning of passerine birds by road salt in the United States and Canada, but little is known about the toxicity of NaCl to songbirds. The objectives of this study were to determine the lethal dose range for NaCl in a representative passerine species (house sparrow [Passer domesticus]); to determine the clinical, physiologic, and pathologic effects of sublethal and lethal oral NaCl exposure; and to assess the potential for recovery after exposure to granular salt or highly concentrated salt solutions. The up-and-down method was used in a pilot study to estimate the lethal oral dose of granular NaCl in wild caught house sparrows. The toxicity of highly concentrated NaCl solution also was investigated. This was followed by an acute dose response study in which house sparrows were dosed orally with granular NaCl at 0, 500, 1,500, 2,500, or 3,500 mg/kg. Sparrows were deprived of water for 6 hr postexposure (PE) in an attempt to mimic specific winter conditions. Groups of three birds at each dose were euthanized at 1, 3, 6, and 12 hr PE, and samples were collected for histopathology and brain and plasma electrolyte analyses. Results indicated an approximate mean lethal dose (LD 50 ) of 3,000-3,500 mg/kg in water-deprived birds, which is similar to mammalian values. House sparrows dosed with a concentrated solution of NaCl generally died at doses of 8,000 mg/kg. Clinical signs observed at Ն1,500 mg/kg included rapid onset (Ͻ30 min) of depression (indicated by reduced activity and reduced response to visual and auditory stimuli), ataxia, inability to fly or perch, and death in as little as 45 min. Birds that survived for 6 hr usually recovered. Plasma Na concentrations Ͼ200 mmol/l were consistently associated with clinical signs. Pathologic lesions consisted of edema and distension of the caudoventral thin muscled region of the gizzard and were observed 1 hr PE in most birds dosed with Ն500 mg/kg. Brain Na concentrations in clinically ill sparrows and those that died of NaCl toxicity ranged from 1,297 to 1,615 (meanϭ1,450; SDϭ115) ppm wet weight or 5,603 to 6,958 (meanϭ6,367; SDϭ454) ppm dry weight, which differed significantly from control birds. No histologic lesions were observed in brain sections of exposed birds, likely reflecting the acute nature of the exposure. However, fluid accumulation beneath the koilin layer of the gizzard was observed in the majority of birds at high dosage levels. These results indicate that passerines ingesting relatively small numbers of road salt granules or small quantities of highly concentrated NaCl solutions are at risk of sodium poisoning.

Chemical Deicer Poisoning was Suspected as a Cause of the 2005-2006 Wintertime Mortality of Small Wild Birds in Hokkaido

“…In deicer-treated chicks, the plasma Na concentration significantly increased and 200 mmol/l was lethal, consistent with previous reports [3,4]. The uptake of 0.1 g deicer was lethal to chicks, and was equivalent to 0.07 g for sparrows on a body weight basis.…”

“…Some chicks showed edematous thickening of the gizzard wall, but no change was observed in the wild birds. Lesions from NaCl (chemical deicer) poisoning have been reported to be transient and may disappear after death [3]. In the winter of 2005-2006, we experienced relatively heavy snowfall and low temperature in compare with ordinal years.…”

“…Factors leading to poisoning include freezing temperature and heavy snowfall in winter, which result in a decrease in water supply and an increase in salt deposited due to stepped-up deicing operations on roads [5]. Recently, a report on the toxicity of sodium chloride (NaCl) to house sparrows (Passer domesticus) was documented [3]. According to the report, sparrows orally given a lethal dose of NaCl showed rapid onset of depression, ataxia and death within 45 min.…”

Nervous signs of salt poisoning in Wistar rats

“…Windingstad et al (1987) showed that brain sodium levels were higher in dead geese suspected with salt poisoning submitted for necropsy than in controls. Bollinger, Mineau, and Wickstrom (2005) explained that 168 H. Fereidoun no histologic lesions were observed in brain sections of exposed birds, likely reflecting acute nature of the exposure to salt. However, fluid accumulation beneath the kaolin layer of the gizzard was observed in the majority of birds at high dosage levels.…”

“…Sodium chloride (NaCl) is the most commonly used deicer on roadways in North America, with approximately 4À5 and 15 million tons used each year in Canada and United States, respectively. Wildlife mortality along roadsides where salt has been applied has been documented (Bollinger, Mineau, and Wickstrom 2005). Sodium levels in groundwaters vary widely, depending upon geological formation.…”