Reducing exposure to high levels of perfluorinated compounds in drinking water improves reproductive outcomes: evidence from an intervention in Minnesota.

BackgroundPer- and polyfluoroalkyl substances (PFASs) have been detected in drinking water supplies around the world and are the subject of intense regulatory debate. While they have been associated with several illnesses, their effects on reproductive outcomes remains uncertain.MethodsWe analyzed birth outcomes in the east Minneapolis-St. Paul metropolitan area from 2002 to 2011, where a portion of the population faced elevated exposure to PFASs due to long-term contamination of drinking water supplies from industrial waste disposal. Installation of a water filtration facility in the highly contaminated city of Oakdale, MN at the end of 2006 resulted in a sharp decrease in exposure to PFASs, creating a "natural experiment". Using a difference-in-differences approach, we compare the changes in birth outcomes before and after water filtration in Oakdale to the changes over the same period in neighboring communities where the treatment of municipal water remained constant.ResultsAverage birth weight and average gestational age were statistically significantly lower in the highly exposed population than in the control area prior to filtration of municipal water supply. The highly exposed population faced increased odds of low birth weight (adjusted odds ratio 1.36, 95% CI 1.25-1.48) and pre-term birth (adjusted odds ratio 1.14, 95% CI 1.09-1.19) relative to the control before filtration, and these differences moderated after filtration. The general fertility rate was also significantly lower in the exposed population (incidence rate ratio 0.73, 95% CI 0.69-0.77) prior to filtration and appeared to be rebounding post-2006.ConclusionsOur findings provide evidence of a causal relationship between filtration of drinking water containing high levels of exposure to PFASs and improved reproductive outcomes

Using Sat solvers for synchronization issues in partial deterministic automata

We approach the task of computing a carefully synchronizing word of minimum length for a given partial deterministic automaton, encoding the problem as an instance of SAT and invoking a SAT solver. Our experimental results demonstrate that this approach gives satisfactory results for automata with up to 100 states even if very modest computational resources are used.Comment: 15 pages, 3 figure

DFAs and PFAs with Long Shortest Synchronizing Word Length

It was conjectured by \v{C}ern\'y in 1964, that a synchronizing DFA on $n$ states always has a shortest synchronizing word of length at most $(n-1)^2$, and he gave a sequence of DFAs for which this bound is reached. Until now a full analysis of all DFAs reaching this bound was only given for $n \leq 4$, and with bounds on the number of symbols for $n \leq 10$. Here we give the full analysis for $n \leq 6$, without bounds on the number of symbols. For PFAs the bound is much higher. For $n \leq 6$ we do a similar analysis as for DFAs and find the maximal shortest synchronizing word lengths, exceeding $(n-1)^2$ for $n =4,5,6$. For arbitrary n we give a construction of a PFA on three symbols with exponential shortest synchronizing word length, giving significantly better bounds than earlier exponential constructions. We give a transformation of this PFA to a PFA on two symbols keeping exponential shortest synchronizing word length, yielding a better bound than applying a similar known transformation.Comment: 16 pages, 2 figures source code adde

Omnipresent Chemicals: TSCA Preemption in the Wake of PFAS Contamination

Over the past few decades, studies addressing the harms of PFAS have gradually progressed, and now scientists believe increased exposure could lead to reproductive defects and a higher risk of cancer. Given the amplified concern surrounding these pervasive chemicals, states are proactively filing lawsuits on behalf of their citizens and enacting legislation to combat this nation-wide contamination epidemic. However, given the 2016 Amendment to the Toxic Substances Control Act of 1976, states looking to regulate the manufacturing or looking to ratify a state- wide ban on the manufacturing of such chemicals may face preemption under actions taken by the United States Environmental Protection Agency. This Note focuses on the possible loss of state autonomy with regards to PFAS regulation. It addresses the issues states might face given the restrictive nature of the newly enacted preemption provisions of the Toxic Substances Control Act, while also examining the Act’s possible deficiencies. Ultimately, recognizing a need for creative solutions outside the scope of manufacturing regulations may provide the best solutions for states to combat these ubiquitous chemicals

Burden of fetal alcohol syndrome in a rural West Coast area of South Africa

Background. Fetal alcohol syndrome (FAS) is common in parts of South Africa; rural residence is a frequently cited risk factor. We conducted a FAS school prevalence survey of an isolated rural community in a West Coast village of Western Cape Province, so obtaining the first directly measured rate, focusing specifically on a South African rural area, of FAS and partial FAS (PFAS). Methods. The study area (Aurora village), a community of about 2 500 people in a grain-producing region, has one primary school. All learners were eligible for study inclusion. Initial anthropometry screening was followed by a diagnostic stage entailing examination by a dysmorphologist for features of FAS, neurodevelopmental assessment, and an interview assessing maternal alcohol consumption. Results. Of 160 learners screened, 78 (49%) were screen-positive, of whom 63 (81%) were clinically assessed for FAS. The overall FAS/PFAS rate among the screened learners was 17.5% (95% confidence interval 12.0 - 24.2%), with 16 (10.0%) children having FAS and 12 (7.5%) PFAS. High rates of stunting, underweight and microcephaly were noted in all learners, especially those with FAS or PFAS. Five (18%) mothers of affected children were deceased by the time of assessment. Conclusion. We describe very high rates of FAS/PFAS in an isolated rural part of the Western Cape that is not located in a viticultural region. Our study suggests that the prevalence of FA S may be very high in isolated communities, or in particular hot-spots. It adds to the growing evidence that FAS/PFAS is a significant, and underestimated, health problem in South Africa. Expanded screening and surveillance programmes, and preventive interventions, are urgently needed

An assessment of organic solvent based equilibrium partitioning methods for predicting the bioconcentration behavior of perfluorinated sulfonic acids, carboxylic acids, and sulfonamides

SPARC, KOWWIN, and ALOGPS octanol-water partitioning (log K~ow~) and distribution (log D) constants were calculated for all C~1~ through C~8~ and the straight chain C~9~ through C~15~ perfluoroalkyl sulfonic acids (PFSAs) and carboxylic acids (PFCAs). Application of five established models for estimating bioconcentration factors (BCFs) were applied to the PFSA and PFCA log K~ow~ and log D data and compared to available field and laboratory BCF data. Wide variability was observed between the methods for estimating log K~ow~ and log D values, ranging up to several log units for particular congeners, and which was further compounded by additional variability introduced by the different BCF equations applied. With the exception of n-perfluorooctanecarboxylic acid (n-PFOA), whose experimental BCF was poorly modeled by all approaches, the experimental BCF values of the other PFSA and PFCA congeners were reasonably approximated by the ALOGPS log P values in combination with any of the five log K~ow~ based BCF equations. The SPARC and KOWWIN log K~ow~ and log D values provided generally less accurate BCF estimates regardless of the BCF equation applied. However, the SPARC K~ow~ values did provide BCF estimates for PFSA congeners with errors <0.3 log units using any of the five BCF equations. Model lipophilic and proteinophilic solvent based distribution constant calculations for the PFSA and PFCA congeners with experimental BCFs exhibited similar relationships with their corresponding BCF values. For longer chain PFCA and PFSA congeners, increasing hydrophobicity of the perfluoroalkyl chain appears to be driving corresponding increases in BCF values. Perfluorooalkyl sulfonamides are expected to display similar chain length and branching pattern influences on BCFs, but no experimental data are currently available upon which to validate the estimated values which range widely between the various approaches by up to 10 log units. The amidic proton acidity on primary and secondary perfluoroalkyl sulfonamides will play a significant role in the partitioning of these compounds with both abiotic and biotic organic matter, and will need to be taken into account when assessing their environmental and biological fate

The minimal probabilistic and quantum finite automata recognizing uncountably many languages with fixed cutpoints

It is known that 2-state binary and 3-state unary probabilistic finite automata and 2-state unary quantum finite automata recognize uncountably many languages with cutpoints. These results have been obtained by associating each recognized language with a cutpoint and then by using the fact that there are uncountably many cutpoints. In this note, we prove the same results for fixed cutpoints: each recognized language is associated with an automaton (i.e., algorithm), and the proofs use the fact that there are uncountably many automata. For each case, we present a new construction.Comment: 12 pages, minor revisions, changing the format to "dmtcs-episciences" styl

Memory effects can make the transmission capability of a communication channel uncomputable

Most communication channels are subjected to noise. One of the goals of Information Theory is to add redundancy in the transmission of information so that the information is transmitted reliably and the amount of information transmitted through the channel is as large as possible. The maximum rate at which reliable transmission is possible is called the capacity. If the channel does not keep memory of its past, the capacity is given by a simple optimization problem and can be efficiently computed. The situation of channels with memory is less clear. Here we show that for channels with memory the capacity cannot be computed to within precision 1/5. Our result holds even if we consider one of the simplest families of such channels -information-stable finite state machine channels-, restrict the input and output of the channel to 4 and 1 bit respectively and allow 6 bits of memory.Comment: Improved presentation and clarified claim