In mammals, cobalt-deficient diets can cause reproductive output to be significantly reduced. Over-exposure of water-soluble cobalt salts has also been found to cause damage in the testicular tissue of male rats and mice.

Exposure to cobalt can occur through oral and inhalation routes. Mammals, including humans, are exposed to natural sources of cobalt in their food, water and atmosphere. In addition to naturally occurring forms of cobalt in the environment, cobalt substances are present in certain occupational settings where cobalt is produced or utilised.

Cobalt deficiency

Cobalt in the chemically distinct form of Vitamin B12 is essential for humans and many non-ruminant mammals. Ruminant domestic mammals, such as cattle, sheep and goats, but also many wild animals (deer, moose, elk, and giraffes, for example) require the cobalt ion as an essential trace element. Cobalt is needed for many aspects of their metabolism, for example the formation of new red blood cells, as well as for their reproductive health. It is common agricultural and veterinary practice to provide cobalt salt supplements to ensure sufficient amounts of cobalt ion for animal growth and good health. Doses of cobalt in diets that are too low (deficient) or too high (over-exposure) have both been reported to have harmful effects. Cobalt-deficient diets are associated with a “wasting disease” in farm ruminants, deer, elk and moose where the animals fail to thrive and their reproductive output is significantly decreased.

Elks grazing
Ruminant mammals require the cobalt ion as an essential trace element

Cobalt over-exposure

Over-exposure to water-soluble cobalt salts (and thus the cobalt ion) has been shown to cause damage to testicular tissue in male rats and mice. The effects are reported by oral exposure to high doses of cobalt chloride and by inhalation exposure to high concentrations of cobalt sulfate and cobalt metal. These studies also reported that sperm number and motility were affected, and at the highest doses tested, fertility in male mice was reduced (as measured by the percentage of fertilised ova).

These effects appear to occur at very high doses and in male mice and rats only. There are no studies with respect to the impact of cobalt on the human reproductive system, nor are there any data on female rats and mice. The cobalt industry has conducted several studies on rats, where the animals were exposed to the highly soluble cobalt dichloride, up to doses which significantly increased the cobalt levels in all tissues. These studies were conducted according to the highest scientific standards (following OECD guidelines, and “Good Laboratory Practice”). Reproductive parameters, such as a thorough examination of both male and female reproductive organs, and hormone levels in the blood, as well as the pre-natal development of rats were studied. No adverse effects were found on any reproductive or developmental parameters, neither in males, females, nor on offspring. Cobalt was taken up and absorbed by the body in those studies, as demonstrated by a significant increase in red blood cells in the exposed animals. This is a well-known effect of cobalt, and it was observed in the absence of any effect on development or fertility.

The question on cobalt’s effect on reproduction will be examined further by industry, in order to ensure that any potential harmful effect is recognised, and safe exposure levels can be set for humans, animals and the environment


This summary is intended to provide general information about the topic under consideration. It does not constitute a complete or comprehensive analysis, and reflects the state of knowledge and information at the time of its preparation. This summary should not be relied upon to treat or address health, environmental, or other conditions.