Organotin compounds

Organotin Compounds

  1. Organotin compounds (OTC) consist of different types with varying properties and industrial applications.

  2. Among the different types of OTC, tributyltin (TBT) and triphenyltin (TPT) have been widely used as biocides in wood preservatives, algicides and molluscicides in antifouling products to coat the bottoms of ship as well as pesticides for agricultural purposes.  Other like dibutyltin (DBT) and di-n-octyltin (DOT) are generally used as polyvinyl chlorides (PVC) stabilisers in many consumer products such as PVC food packaging materials.

Public Health Significance of Organotin Compounds

  1. Through leaching from the antifouling paint used in boat and ship and other marine equipment, from the PVC products disposed into sanitary landfills, as well as from the runoff of agricultural fields, these compounds could be introduced into our estuarine and marine ecosystems.
  2. OTC are relatively persistent in the environment and have a tendency to bioaccumlate in the food chain. The general public is exposed to OTC mostly through intake of fish and other aquatic products.
  3. Other possible sources of dietary exposure could be from pesticides, additives used in plastics and other food contact materials.  However, according to overseas studies, the levels of OTC detected in foods other than aquatic products such as cereals, meat, fruits and vegetables are relatively low.

Toxicity of Organotin Compounds

  1. Although OTC had been found to affect the immune system, cause endocrine disruption and have reproductive and developmental effects in animal studies, there is currently no sufficient data to prove that OTC will cause health concerns in humans.
  2. The Joint FAO/WHO Expert Committee on Food Additives (JECFA) has not established any health based guidance value (HBGV) for OTC, nor has the Codex Alimentarius Commission (Codex) established any standard for OTC in food.

  3. The European Food Safety Authority (EFSA) has established a HBGV for the group of TBT, TPT, DBT and DOT compounds in 2004, which is equivalent to 0.1 mcg/kg bw per day when expressed as Tin(Sn)).

Situation in Hong Kong  

  1. In 2018, the Centre for Food Safety (CFS) has conducted a risk assessment study to estimate the risk from dietary exposure to OTC of Hong Kong adult population from consumption of aquatic products including marine and fresh water fish, crustaceans, and molluscs from local markets. The results showed that OTC were detected in 60% of 341 aquatic product samples taken.  The estimated dietary exposure to OTC for the average and high consumers were 0.020 mcg/kg bw/day as Sn and 0.057 mcg/kg bw/day as Sn respectively, accounted for 20% and 57%, respectively, of the HBGV established by EFSA.  The food group “fish” was the major contributor to the OTC dietary exposure of the local population.

  2. Since the dietary exposures of both the average and high consumers of the local adult population to the OTC were below the HBGV, adverse health outcome due to OTC exposure of the Hong Kong adult population from aquatic products commonly available at local markets was unlikely.

  3. Reduction of OTC in aquatic products relies mainly on the control of their use and release in order to safeguard the marine ecosystem and human health. With the increasing number of places including Hong Kong which restrict the use of OTC in antifouling paints for ships and pesticides, OTC in the environment are expected to be in a decreasing trend.

Advice to Consumers

  1. The public is advised to maintain a balanced and varied diet which included a wide variety of meat, vegetables and fruits so as to avoid excessive exposure to any contaminants from a small range of food items.
  2. Fish contain many essential nutrients, such as omega-3 fatty acids and high quality proteins, moderate consumption of a variety of fish is recommended.

Risk Assessment Section
Centre for Food Safety 
 April 2019