Housed pigs are often exposed to elevated concentrations of atmospheric ammonia. This aerial pollutant is widely considered to be an environmental stressor that also predisposes to reduced growth rates and poor health, although evidence to support this view is limited. Hepatic gene expression is very responsive to stress and metabolic effects. Two batches of growing pigs were therefore exposed to a nominal concentration of atmospheric ammonia of either 5 ppm (low) or 20 ppm (high) from 4 weeks of age for 15 weeks. Growth rates were monitored. Samples of liver were taken after slaughter (at ∼19 weeks of age). Samples from the second batch were analysed for global gene expression using 23 K Affymetrix GeneChip porcine genome arrays. Samples from both batches were subsequently tested for five candidate genes using quantitative real-time PCR (qPCR). The array analysis failed to detect any significant changes in hepatic gene expression following chronic exposure to atmospheric ammonia. Animals clustered into two main groups but this was not related to the experimental treatment. There was also no difference in growth rates between groups. The qPCR analyses validated the array results by showing similar fold changes in gene expression to the arrays. They revealed a significant batch effect in expression of lipin 1 (LPIN1), Chemokine (C-X-C motif) ligand 14 (CXCL14), serine dehydratase (SDS) and hepcidin antimicrobial peptide (HAMP). Only CXCL14, a chemotactic cytokine for monocytes, was significantly down-regulated in response to ammonia. As chronic exposure to atmospheric ammonia did not have a clear influence on hepatic gene expression, this finding implies that 20 ppm of atmospheric ammonia did not pose a significant material risk to the health or metabolism of housed pigs.

Pour des raisons d'efficacité opérationnelle, la CIPR a bâti un système dosimétrique s'appuyant sur l'additivité des effets sur la santé quelle que soit la nature du rayonnement et que l'exposition soit d'origine externe ou interne à l'individu exposé. Ce système a rempli son rôle, le bilan de la radioprotection est aujourd’hui jugé bon. Aujourd'hui, le challenge posé à l'énergie nucléaire est de faire la démonstration que la gestion de ses déchets éventuellement stockés en profondeur sera sans danger pour les générations futures. Le scénario envisagé est lié au retour vers la biosphère avec pour conséquence une contamination interne par ingestion de radionucléides à vie longue. Le système de protection radiologique actuel est-il adapté à ce scénario d’ingestion chronique ? Que signifie une irradiation alpha ? Que sait-on vraiment en terme dosimétriques et de risques de la chronicité des expositions ? Autant de questions pour lesquelles nous n'avons pas toujours la réponse et qu'il faut donc poser au moment où l'on préconise un dialogue avec les parties prenantes, d’autant plus que de récentes observation scientifiques remettent en cause bien des certitudes. De nouveaux programmes de recherche en radiotoxicologie sont absolument nécessaires pour répondre à ces questions légitimes, l'exemple de la démarche de l'industrie pharmaceutique pour l'obtention des autorisations de mise sur le marché des médicaments est à méditer.

For dose assessment following chronic or accidental inhalation of radioactive aerosols, the dosimetric models of the International Commission on Radiological Protection (ICRP) provide dose coefficients, retention and excretion functions. Unknown date or dates of intake is the major source of uncertainty in dose assessment during routine monitoring of nuclear workers. The two assumptions commonly made in dose assessment from an unknown time pattern of intake have been tested experimentally with a model of repeated inhalation by rats. The hypothetical intake derived from lung measurement was relatively reliable under the two hypotheses. The hypothetical intake derived from excreta measurement depended on the choice of hypothesis and on the real time pattern of intake.