Safety assessment and risk–benefit analysis of the use of azodicarbonamide in baby food jar closure technology: Putting trace levels of semicarbazide exposure into perspective – A review

Abstract

The discovery of trace levels of semicarbazide (SEM) in bottled foods (especially baby foods) led to a consideration of the safety of this hydrazine compound by regulatory agencies worldwide. Azodicarbonamide, which is used in the jar-sealing technology known as Press On-Twist Off (or Push-Twist/PT) closures for the formation of a hermetic, plastisol seal, partially degrades with the heat of processing to form trace amounts of SEM. This review has evaluated the potential toxicological risks of resulting exposure to SEM and also the benefit of the PT technology (with azodicarbonamide) in the context of possible microbial contamination. It also considers the potential impact on infant nutrition if parents come to the conclusion that commercial baby foods are unsafe. SEM shows limited genotoxicity in vitro that is largely prevented by the presence of mammalian metabolic enzymes. Negative results were found in vivo in DNA alkaline elution, unscheduled DNA synthesis and micronucleus assays. This pattern is in contrast to the genotoxic hydrazines that also have been shown to cause tumours. Carcinogenicity studies of SEM are of limited quality, show a questionable weak effect in mice at high doses, which are not relevant to human exposure at trace levels, and show no effect in the rat. The IARC has assigned SEM as Group 3, 'Not classifiable as to its carcinogenicity to humans'. Based on estimates of exposure to infants consuming baby foods (with the assumption of SEM levels at the 95th percentile of 20 ng g(-1) in all of the consumed 'ready-to-eat' foods) compared with a no observed adverse effect level (NOAEL) in developmental toxicity studies, the margin of safety is more than 21 000. Since the risk of an adverse effect is negligible, it is clear that any theoretical risk is outweighed by the benefits of continuing use of the PT closure (with azodicarbonamide blowing agent) to ensure both the microbial integrity and availability of commercial baby foods as a valuable source of infant nutrition.

Packaged food intake by British children aged 0 to 6 years

“…Examples of substances that have been found to migrate from food-contact materials or articles in recent years include: semicarbazide from seals used in the 'press-on, twist off' metal lids on glass jars (Nestmann et al 2005); 2-isopropylthioxanthone (ITX) as a set-off from printing into infant formula and fruit juices (Rothenbacher et al 2007); formaldehyde from melamine ware (Bradley et al 2005); and benzophenone from printed packaging (Food Standards Agency (FSA) 2006). These are substances for which a specific safety assessment was required following notification through the European Union Rapid Alert System for Food and Feed (RASFF).…”

Food Safety

“…Semicarbazide is detectable in essentially all foods sold in glass jars, but baby foods were found to contain the highest concentrations (up to 54µg/kg). The dietary exposure from baby food was estimated to be 0.5µg/kg bw per day for 0-12-month-old babies in the USA; 0.4 and 0.66µg/kg bw per day for Canadian babies aged 1-3 months and 6-9 months, respectively; and between 0.23 and 0.53µg/kg bw per day for European babies [111]. In laboratory animals, semicarbazide exposure in utero or postnatally inhibits bone mineralization and leads to skeletal deformities.…”

Exposure assessment of chemicals from packaging materials in foods: a review

“…Metal lids used in glass jars may also be a source of potential contaminants: semicarbazide in baby food jars, resulting from degradation of azodicarbonamide used as blowing agent, and epoxidised soybean oil (ESBO) a plasticizer used in the plastisol gasket (Nestmann et al, 2005). EFSA recommended the decrease of the legal specific migration limit (SML) for ESBO, for infants food packaging applications, from 60 to 30 mg/kg of food or food simulant (Directive 2005/72).…”