Comparison of the effects of N-nitrosodimethylamine on pregnant and nonpregnant Holtzman rats

Occurrence of N-nitrosamines in the atmosphere and human health risk: A case study in an urban area of Chuncheon, Gangwon State, South Korea

This study aimed to investigate the occurrence of eight nitrosamines (NAs) in particulate (PM2.5) and gaseous phases and assess the human health risk associated with these compounds in an urban area of Chuncheon, Gangwon State, South Korea, across four sampling seasons. The findings revealed that the total concentrations of eight NAs measured during the sampling period exceeded the public health recommendation of 0.3 ng/m3 provided by the Norwegian Institute of Public Health, indicating a potential human health risk from NA exposures. In particular, the average total NA concentration observed in the gaseous samples during the winter of 2021 was 18.1 ± 6.46 ng/m3. The primary emission sources could potentially impact the concentrations of NAs in the atmosphere due to their significant positive correlation with primary emission species such as NO2, CO, and SO2. Moreover, the levels of particulate NAs during the summer were negatively correlated with O3, suggesting that their formation might be influenced by ozonation in the aqueous aerosol phase. In addition, the total NA concentrations measured in the gaseous phase were four to six times higher than those measured in the PM2.5 phase throughout the sampling period. Thus, domestic sources have the potential to impact the pollution levels of the research area more significantly than long-range atmospheric transport. In particular, the highest concentrations of NAs in the gas phase were observed during the winter, while the lowest concentrations were recorded in the summer, possibly influenced by photolysis. Nevertheless, the study suggested that tertiary amines might contribute to the presence of gaseous NAs in sunlight. Consequently, further studies focusing on the occurrence of tertiary amines in the gas phase should be considered. The cumulative lifetime cancer risks estimated from inhalation exposure exceeded the acceptable risk level of 10⁻6 for all age groups across all four seasons. Therefore, it is crucial to implement effective control measures to mitigate potential health risks associated with exposure to NAs.

Risk assessment of N-nitrosamines in food

EFSA was asked for a scientific opinion on the risks to public health related to the presence of N-nitrosamines (N-NAs) in food. The risk assessment was confined to those 10 carcinogenic N-NAs occurring in food (TCNAs), i.e. NDMA, NMEA, NDEA, NDPA, NDBA, NMA, NSAR, NMOR, NPIP and NPYR. N-NAs are genotoxic and induce liver tumours in rodents. The in vivo data available to derive potency factors are limited, and therefore, equal potency of TCNAs was assumed. The lower confidence limit of the benchmark dose at 10% (BMDL10) was 10 μg/kg body weight (bw) per day, derived from the incidence of rat liver tumours (benign and malignant) induced by NDEA and used in a margin of exposure (MOE) approach. Analytical results on the occurrence of N-NAs were extracted from the EFSA occurrence database (n = 2,817) and the literature (n = 4,003). Occurrence data were available for five food categories across TCNAs. Dietary exposure was assessed for two scenarios, excluding (scenario 1) and including (scenario 2) cooked unprocessed meat and fish. TCNAs exposure ranged from 0 to 208.9 ng/kg bw per day across surveys, age groups and scenarios. 'Meat and meat products' is the main food category contributing to TCNA exposure. MOEs ranged from 3,337 to 48 at the P95 exposure excluding some infant surveys with P95 exposure equal to zero. Two major uncertainties were (i) the high number of left censored data and (ii) the lack of data on important food categories. The CONTAM Panel concluded that the MOE for TCNAs at the P95 exposure is highly likely (98-100% certain) to be less than 10,000 for all age groups, which raises a health concern.

Developmental and neurobehavioral assessment of low-dose N-nitrosodimethylamine (NDMA) using zebrafish embryo bioassay

N-nitrosodimethylamine (NDMA) is one of the emerging nitrogenous disinfection by-products (DBPs) with probable cytotoxicity, genotoxicity, and carcinogenesis. Its potential toxicological effects have drawn considerable attention but remain inadequately known. Here two methods, including developmental toxicity evaluation and neurobehavioral toxicity evaluation, were used and compared to investigate the safety of low-dose (0, 0.1, 1, 10, 100 μg/L) NDMA exposure to embryo-larval stage of zebrafish. Results showed that the survival and malformation rate of larvae at 6-day post fertilization (dpf) and the hatching rates at 48-h post fertilization (hpf) and 72 hpf in treatment groups had no significant difference with the control group, indicating that the tested NDMA doses were not developmentally toxic. Differently, the changes of neurobehavioral indicators performed more sensitivity. For example, 100 μg/L NDMA exposure induced locomotor hyperactivity at 7 dpf and induced an increasing effect on the relative path angle value. Further, relative value of path angle had more consistency with locomotion results compared with absolute value, indicating that relative value of path angle may be more suitable for the safety evaluation of low-dose NDMA exposure. This work supported that zebrafish neurobehavioral test is a powerful tool in the safety assessment of low-dose NDMA exposure and also has the potential to evaluate the safety of other DBPs.