Barry S. Lynch

Carcinogenicity of Monochloro-1,2-Propanediol (α-Chlorohydrin, 3-MCPD)

3-Monochloro-1,2-propanediol (3-MCPD) is a by-product found in trace amounts, generally less than 1 mg/kg (<1 ppm), in hydrolyzed vegetable protein produced through acid hydrolysis. In a chronic study with F344 rats, high doses of 3-MCPD produced benign renal tumors in both sexes and Leydig-cell and mammary tumors in males. 3-MCPD is genotoxic in vitro, but there is no evidence of genotoxicity in vivo. There is some question about the mechanism responsible for the carcinogenicity of 3-MCPD in certain species. Here we present a critical review of the toxicological, metabolic, and mechanistic data on 3-MCPD. On the basis of this review, the tumors reported in F344 rats are concluded to have developed as a result of nongenotoxic mechanisms and are considered not to be relevant to humans exposed to trace amounts of 3-MCPD. This conclusion was based on the lack of carcinogenicity of 3-MCPD in mice or Sprague-Dawley rats; the benign nature of the tumors involved; the dependence of the Leydig-cell and mammary tumors on species-and strain-dependent mechanisms involving chronic changes in hormone balance; the association of the renal tumors with chronic nephropathy and nephrotoxicity; and differences between bacterial and mammalian systems in the metabolism of 3-MCPD that likely account for its genotoxic activity in certain in vitro test systems. At trace levels in foods, 3 MCPD is considered not to pose a carcinogenic risk to humans.

A reassessment of risk associated with dietary intake of ochratoxin A based on a lifetime exposure model

Mycotoxins, such as ochratoxin A (OTA), can occur from fungal growth on foods. OTA is considered a possible risk factor for adverse renal effects in humans based on renal tumors in male rats. For risk mitigation, Health Canada proposed maximum limits (MLs) for OTA based largely on a comparative risk assessment conducted by Health Canada (), in which analytical data of OTA in foods were used to determine the possible impact adopting MLs may have on OTA risks. The EU MLs were used for comparison and resultant risk was determined based on age–sex strata groups. These data were reevaluated here to determine comparative risk on a lifetime basis instead of age strata. Also, as there is scientific disagreement over the mechanism of OTA-induced renal tumors, mechanistic data were revisited. On a lifetime basis, risks associated with dietary exposure were found to be negligible, even without MLs, with dietary exposures to OTA three to four orders of magnitude below the pivotal animal LOAEL and the TD05. Our review of the mechanistic data supported a threshold-based mechanism as the most plausible. In particular, OTA was negative in genotoxicity assays with the highest specificity and levels of DNA adducts were very low and not typical of genotoxic carcinogens. In conclusion, OTA exposures from Canadian foods do not present a significant cancer risk.

Rodent carcinogenicity tests need be no longer than 18 months: an analysis based on 210 chemicals in the IARC monographs.

The IARC Monographs (Vols 1-70) were studied to determine the time of onset of treatment-related tumorigenicity in long-term rodent studies for chemicals classified by IARC as having sufficient evidence of carcinogenicity in animals. The analysis excluded studies on metals and their salts, studies on particulates, studies by parenteral routes of administration that resulted in tumours only at the site of exposure, and studies that did not approximate to the current standard long-term rodent carcinogenicity bioassay, for instance transplacental or multigeneration studies, initiator-promoter studies, lung tumour assays in Strain A mice and studies in newborn animals. Data from a total of 210 chemicals revealed that, overall, evidence of treatment-related tumorigenicity was first apparent within 12 months for 66% of the chemicals and for only 7% were studies of longer than 18 months necessary. All IARC Group 1 chemicals were detected in animals within 18 months, and most within 12 months. Most of the tumour types that required more than 18 months for detection were of dubious relevance to human risk assessment. Termination of rodent carcinogenicity studies at 18 months or earlier would greatly reduce the complications that arise in interpreting the findings in aged animals which often have defective hepatic or renal function and would also markedly reduce the time required for histopathological examination of dozens of tissues taken from the approximately 500 animals routinely employed in these studies.

Technological challenges of addressing new and more complex migrating products from novel food packaging materials.

The risk assessment of migration products resulting from packaging material has and continues to pose a difficult challenge. In most jurisdictions, there are regulatory requirements for the approval or notification of food contact substances that will be used in packaging. These processes generally require risk assessment to ensure safety concerns are addressed. The science of assessing food contact materials was instrumental in the development of the concept of Threshold of Regulation and the Threshold of Toxicological Concern procedures. While the risk assessment process is in place, the technology of food packaging continues to evolve to include new initiatives, such as the inclusion of antimicrobial substances or enzyme systems to prevent spoilage, use of plastic packaging intended to remain on foods as they are being cooked, to the introduction of more rigid, stable and reusable materials, and active packaging to extend the shelf-life of food. Each new technology brings with it the potential for exposure to new and possibly novel substances as a result of migration, interaction with other chemical packaging components, or, in the case of plastics now used in direct cooking of products, degradation products formed during heating. Furthermore, the presence of trace levels of certain chemicals from packaging that were once accepted as being of low risk based on traditional toxicology studies are being challenged on the basis of reports of adverse effects, particularly with respect to endocrine disruption, alleged to occur at very low doses. A recent example is the case of bisphenol A. The way forward to assess new packaging technologies and reports of very low dose effects in non-standard studies of food contact substances is likely to remain controversial. However, the risk assessment paradigm is sufficiently robust and flexible to be adapted to meet these challenges. The use of the Threshold of Regulation and the Threshold of Toxicological Concern concepts may play a critical role in the risk assessment of new food packaging technologies in the future.

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

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.

Genotoxicity of pyrroloquinoline quinone (PQQ) disodium salt (BioPQQ

The genotoxic potential of pyrroloquinoline quinone (PQQ) disodium salt (BioPQQ™) was evaluated in a battery of genotoxicity tests. The results of the bacterial mutation assay (Ames test) were negative. Weak positive results were obtained in 2 separate in vitro chromosomal aberration test in Chinese hamster lung (CHL) fibroblasts. Upon testing in an in vitro chromosomal aberration test in human peripheral blood lymphocytes, no genotoxic activity of PQQ was noted. In the in vivo micronucleus assay in mice, PQQ at doses up to 2,000 mg/kg body weight demonstrated that no genotoxic effects are expressed in vivo in bone marrow erythrocytes. The weak responses in the in vitro test CHL cells were considered of little relevance under conditions of likely human exposure. PQQ disodium was concluded to have no genotoxic activity in vivo.

Subchronic toxicity evaluation of potato protein isolates.

The protein content of potatoes has a high nutritional value on par with eggs and soybeans. As a result, processed potato protein isolates may have commercial value for addition to other food products to increase protein content. A manufacturing process has been developed to produce total potato (TP), as well as low (LMW) and high molecular (HMW) weight, protein isolates as food ingredients. To assess the safety of these isolates, groups of 10 Wistar rats/sex were administered dietary admixtures containing 15% HMW, 7.5% LMW or 15% TP protein isolates for a period of 90days. There was no effect of treatment on clinical signs, mortality, body weight and body weight gain. No biologically significant changes occurred in hematological and clinical chemistry parameters. No statistically significant changes in organ weights were recorded. Histopathological analyses revealed no clear, treatment-related changes. A slight increase in the incidence, but not severity, of vacuolation of the zona fasciculate of the adrenal gland was noted in males of the 15% HMW and 7.5% LMW groups. The finding was not considered adverse or ascribed any toxicological significance. Overall, HMW, LMW, and TP protein isolates were well-tolerated and without adverse effect. These data support the safety of potato protein isolates.

Subchronic toxicity evaluation of aloesin

Aloesin, an aromatic chromone present in various Aloe species, shows potential beneficial effects on indices related to pre-diabetic states, including metabolic syndrome. Aloesin may have utility as a functional food ingredient. As part of a program to assess its safety, aloesin was administered by oral gavage at doses of 250, 500, and 1000 mg/kg body weight/day to groups of 10 male and 10 female Sprague-Dawley rats for 90 days. Treatment was not associated with mortality and appeared to be well tolerated. There were no toxicologically or statistically significant changes in body weight gain or in feed and water consumption. A few statistically significant changes in serum biochemistry and hematology parameters were noted, but all were mild in nature, were confined to one sex, and/or did not show dose-response relationships. Urinalysis revealed dose-dependent increases in urinary ketones. This result was due to the presence of aloesin, which possesses ketone functionalities, in the urine and not due to a systemic effect. There was no effect of treatment on organ weights or on the results of the histopathological examinations. The no-observed-adverse-effect level was considered to be 1000 mg/kg body weight/day, the highest dose tested. The results support potential use of aloesin as a functional food ingredient.

In vitro and in vivo assessment of the genotoxic activity of aloesin

Aloesin is a chromone that is a component of Aloe spp. It may have potential as a functional food ingredient as it has been shown to likely have beneficial effects in persons in a pre-diabetic state or who have metabolic syndrome. In this study the safety of aloesin has been evaluated using a series of in vitro and in vivo genotoxicity assays including, bacterial mutation, mammalian cell cytogenetic, and mouse micronucleus tests. Aloesin did not induce reverse mutations in Salmonella typhimurium and Escherichia coli at any of the tested dose levels up to 10,000 μg/plate. Similarly, aloesin did not increase the incidence of chromosome aberrations when incubated with Chinese hamster lung cells at any of the tested concentrations up to 10,000 μg/mL. In vivo, there was no effect of aloesin on the incidence of micronucleated erythrocytes following oral administration on two consecutive days at doses up to 5000 mg/kg body weight. There was no evidence of toxicity to bone marrow. The results of these studies demonstrate that aloesin is without genotoxic potential.

Genetic and acute toxicological evaluation of an algal oil containing eicosapentaenoic acid (EPA) and palmitoleic acid

Algal strains of Nannochloropsis sp. were developed, optimized, cultivated and harvested to produce a unique composition of algal oil ethyl esters (Algal-EE) that are naturally high in eicosapentaenoic acid (EPA, 23-30%) and palmitoleic acid (20-25%), and contain no docosahexaenoic acid (DHA). Algal-EE was evaluated for mutagenic activity (Ames bacterial reverse mutation, in vitro mammalian chromosome aberration, in vivo micronucleus test) and for acute oral toxicity in Sprague-Dawley rats. In the acute toxicity study, rats received a single oral gavaged dose of Algal-EE (2000 mg/kg body weight). Clinical observations were made for 14 days before sacrifice on Day 15. Macroscopic evaluation involved the examination of all organs in the cranial, thoracic, and abdominal cavities. Algal-EE showed no evidence of mutagenicity, did not produce an increase in the frequency of structural chromosome aberrations, and did not cause an increase in the induction of micronucleated polychromatic erythrocytes. There were no macroscopic abnormalities. Algal-EE up to 2000 mg/kg body weight did not affect body weight, organ appearance or produce any toxic-related signs of morbidity. The acute median lethal dose (LD50) of Algal-EE was >2000 mg/kg body weight. Based on these assays, Algal-EE does not appear to have any genetic or acute oral toxicity.