Potency grading in carcinogen classification

Impact of oil contamination of grey forest soil on its nutrient status and plant safety

The study was carried out in the Republic of Tatarstan (Volga Federal District of the Russian Federation) in grey forest middle loamy soil with weak acid reaction of the medium, low humus content, increased content of labile forms of phosphorus and potassium. The soil was deliberately contaminated with oil at a dose of 25 l/m2. There is close positive linear relationship (R2=0.845) between the amount of bens(a)pyrene (BP) and petroleum substances in soil. The BP content in oil-contaminated horizons (0–15, 15–30, 30–45 cm) of soil exceeded the maximum allowable concentration by 10.5–19.5 times that demonstrates a serious threat to vegetable products growing on oil-contaminated lands. Due to oil contamination, the content of most labile forms of nutrients (N, P, K, B, Mo, Zn) decreased and others remained unchanged (Cu, Co) or increased (Mn). At the same time, these changes were not so significant, because the groups of soil supply with labile forms of nutrients, except phosphorus and potassium, did not change under the influence of oil.

Critical aspects in reproductive and developmental toxicity testing of environmental chemicals

The process of toxicity testing of environmental chemicals is ruled by a framework of guidelines (OECD, OPPTS, etc.). The present paper will describe the process from the biological tests for environmental chemicals up to potential labelling and will focus on some critical aspects in this cascade of events. It is also the aim of this paper to give an overview of the existing documents and draft documents relevant for this field and available in the internet. Based on the current situation, the following points are discussed as critical issues: life stage considerations and their implications on testing, usefulness of investigations in juvenile animals, requirements for ADME studies, design and endpoints in fertility studies, use and usefulness of developmental milestones, performance of special studies versus one-study-design, considerations on transplacental carcinogenicity and early aging, significance of maternal/parental toxicity, application of triggers to justify studies, inclusion of new endpoints into test guidelines, and test strategies applied. Based on this, the usefulness of risk considerations in the current EU classification system for toxicity to reproduction as well as potency considerations will be discussed and suggestions will be made to improve the basic requirements for chemical testing which have remained relatively unchanged over the past 20 years.

A rationale for determining, testing, and controlling specific impurities in pharmaceuticals that possess potential for genotoxicity

The synthesis of pharmaceutical products frequently involves the use of reactive reagents and the formation of intermediates and by-products. Low levels of some of these may be present in the final drug substance and drug product as impurities. Such chemically reactive impurities may have at the same time the potential for unwanted toxicities including genotoxicity and carcinogenicity and hence can have an impact on product risk assessment. This paper outlines a procedure for testing, classification, qualification, toxicological risk assessment, and control of impurities possessing genotoxic potential in pharmaceutical products. Referencing accepted principles of cancer risk assessment, this document proposes a staged threshold of toxicological concern (TTC) approach for the intake of genotoxic impurities over various periods of exposure. This staged TTC is based on knowledge about tumorigenic potency of a wide range of genotoxic carcinogens and can be used for genotoxic compounds, for which cancer data are limited or not available. The delineated acceptable daily intake values of between approximately 1.5 microg/day for approximately lifetime intake and approximately 120 microg/day for < or = 1 month are virtually safe doses. Based on sound scientific reasoning, these virtually safe intake values do not pose an unacceptable risk to either human volunteers or patients at any stage of clinical development and marketing of a pharmaceutical product. The intake levels are estimated to give an excess cancer risk of 1 in 100,000 to 1 in a million over a lifetime, and are extremely conservative given the current lifetime cancer risk in the population of over 1 in 4 (http://seer.cancer.gov/statfacts/html.all.html). The proposals in this document apply to all clinical routes of administration and to compounds at all stages of clinical development. It is important to note that certain types of products, such as those for life-threatening indications for which there are no safer alternatives, allow for special considerations using adaptations of the principles outlined in this paper.

Using carcinogenic potency ranking to assign air contaminants to emission classes

Carcinogenic air contaminants are assigned to emission classes with different emission limits on the basis of their inhalation carcinogenic potency within the revised form of the German First General Administrative Regulation Pertaining to the Federal Emission Control Law (Technical Instructions on Air Quality Control-TA Luft). Accordingly, compounds with high carcinogenic potency are regulated more strictly than less potent substances. The data on carcinogenic properties are heterogeneous. Twenty-five substances or substance groups have been scrutinized and a procedure has been developed to rank these chemicals according to their carcinogenic potency. For 14 substances well-founded unit risk estimates were available to allow assignment of these air contaminants to emission classes. Unit risk estimates for bromoethane, 2-butanone oxime, and o-toluidine were derived using the ED(10)/LED(10) method based on animal studies. For several substances no qualified unit risk estimates or carcinogenicity studies were available to estimate carcinogenic potency after inhalation. Carcinogenic potency of these substances was approximated using two simple methods, T25 and CELmin.