Bacterial diversity across four drinking water distribution systems in Croatia: impacts of water management practices and disinfection by-products.

Several factors may impact bacterial diversity in drinking water distribution systems (DWDSs) including the origin of the raw water, the water treatment technologies, and the disinfection practices applied. 16S rRNA metabarcoding was used for the in-depth characterization of bacterial communities in the four studied Croatian DWDSs (A, B, C, D) two of which had residual disinfectant (A, B) and two were without (C, D), while only B utilized the conventional water treatment technology. Significantly higher diversity and species richness were evidenced in non-disinfected DWDSs (p<0.05) compared to disinfected DWDSs. The phylum Proteobacteria was the most abundant in all the DWDSs, being proportionately higher in non-disinfected systems (p<0.05). The most abundant genera in DWDS-A Mycobacterium and Sphingomonas both positively correlated, whereas Lactobacillus negatively correlated with the concentration of disinfection by-products (DBPs) as a sum of haloacetic acids (HAAs). Conversely, the genus Ralstonia positively correlated with the individual DBP dichloroacetic acid. These results indicate that genera Sphingomonas, Mycobacterium, Lactobacillus and Ralstonia could have an effect on promoting the formation of DBPs, in a similar manner to how negatively correlated taxa may influence their degradation.

Mixing of arsenic-rich groundwater and surface water in drinking water distribution systems: Implications for contaminants, disinfection byproducts and organic components.

The utilization of groundwaters containing high levels of arsenic (As) for drinking water purposes presents major health and economic challenges for water utilities. One low-cost approach is to mix arsenic-rich groundwater (GW) with arsenic-free surface waters (SW) to achieve acceptable As levels. In this study we investigated the effect of different mixing ratios on water quality in an eastern Croatian water distribution system (WDS). To investigate the effects of mixing on drinking water quality, we measured the organic matter (OM) composition, disinfection byproduct (DBP) and metal concentrations in differently mixed ratios of GW and SW within the WDS. Fluorescence analysis revealed that the GW and SW had similar OM composition, with an almost equal ratio of humic- and protein-like OM throughout the WDS despite fluorescence indices revealing slightly different OM sources between the two water types. The tyrosine-like OM component was more variable, increasing during warmer months and towards the end of the WDS, most likely due to enhanced biofilm formation. Arsenic concentrations decreased to below 10 µg/L in the second half of the sampling campaign. Acceptable water quality was achieved after a period of destabilization and solubilization of loose deposits within the WDS resulting in their mobilization caused by water quality changes. Principal component and classification analysis, regression models and Spearman correlation coefficients revealed an association between As, OM and DBP concentrations with these correlations suggestive of their role in As mobilization in the WDS. Changing source waters, with different OM content and characteristics, corresponded to variable As release within the WDS.

Effects of changing supply water quality on drinking water distribution networks: Changes in NOM optical properties, disinfection byproduct formation, and Mn deposition and release.

Field studies were conducted in a Croatian city supplied by two distinct groundwater sources (referred to as A and B) to investigate both the effects of changing water source on the water quality in the drinking water supply system, as well as to further understand discoloration events that occurred in city locations that switched water from source A to B. The water treatment processes at site A were found to alter organic matter (OM) characteristics, removing humic substances while enhancing protein-derived (tryptophan) content. Although the humic-like component predominated in raw waters, microbially/protein-derived components were found to increase throughout the distribution networks of both systems. Disinfection byproducts (DBPs) such as total trihalomethane (TTHM) and total haloacetic acid (THAA) were prevalent in water distribution system (WDS)-A, which correlated with elevated OM content as well as re-chlorination with hypochlorite (NaOCl). Our field study revealed that THMs were more readily formed than HAAs during ClO2 treatment. Unsurprisingly, chlorite concentrations were generally higher than chlorate concentrations during ClO2 treatment, whereas (secondary) NaOCl disinfection contributed to higher chlorate production. Principal component analysis indicated that variable pH values and humic-like OM could affect Mn, As and Al concentrations at the consumer's tap. Our results suggested that although Mn concentrations complied with regulations at WDS-B and were below 50 µg/L after disinfection, Mn was oxidized and formed particulate Mn oxides capable of causing discoloration events depending on prevailing network physico-chemical and hydraulic conditions. Aluminium also appears to be released during hydraulic disturbances from extensive deposits within the network. Thermodynamic calculations showed that Mn-oxidation was strongly dependent upon the ORP, and to lesser extent the pH value. Collectively, our results confirm that ensuring the provision of safe drinking waters to consumers requires an understanding of water quality across entire distribution networks in addition to any routine post-treatment monitoring.

Disinfection by-products in Croatian drinking water supplies with special emphasis on the water supply network in the city of Zagreb.

The occurrence of disinfection by-products (DBPs) was investigated in 48 drinking water systems across Croatia. Eleven DBPs were studied: chlorite (ClO2-), chlorate (ClO3-), four trihalomethanes (THMs), and five haloacetic acids (HAAs). Furthermore, an intensive sampling program was conducted in the distribution system in the city of Zagreb where, aside from DBP analyses, natural organic matter (NOM) was characterized using fluorescence spectroscopy. In the drinking waters examined across Croatia, DBP values were found in the range from 0.7 µg/L to 32.8 µg/L for THMs, below LOQ to 17.2 µg/L for HAAs (primarily di- and trichloroacetic acids), below LOQ to 720 µg/L for ClO2- and below LOQ to 431 µg/L for ClO3-. The results obtained showed higher chlorite concentrations in the systems treated with hypochlorite compared to systems treated with chlorine dioxide. DBPs in the Zagreb distribution network were generally low (the average values were below 6 µg/L and 2 µg/L for total THM and total HAA respectively). In contrast to our observations throughout Croatia, dibromoacetic acid (DBAA) was found to be the predominant HAA within Zagreb, most likely due to the degradation of chlorinated carboxylates (di-/tri-chloroacetic) in the network. Characterization of NOM by Parallel Factor Analysis (PARAFAC) fluorescence spectroscopy across the Zagreb network showed distinct temporal variations arising from groundwater inputs, as evident from variable humic-, tyrosine-, and tryptophan-like peaks. Statistical correlations between fluorescence data and DBPs highlight its potential for monitoring the presence of DBPs in distribution networks.

[Disability, the risk of disability and changes in work capacity-- unacceptable conditions for insurance in occupational injuries and diseases]. / Invalidnost, opasnost od invalidnosti i izmijenjena radna sposobnost--neodrziv uvjet osiguranja od ozljede na radu i profesionalne bolesti.

According to Croatian legislation disability, risk of disability and altered work capacity are prerequisites for recognition of job injuries, occupational diseases, and, consequently, of the worker's special rights. That is also valid for all areas of insurance. The legislation, if applied, would make it impossible for a great number of insured workers to realize their particular rights based on work related health damage, especially in the field of health insurance and reinsurance of health care costs. Health insurance boards, along with insurance companies, manage by evading the condition of disability, risk of disability and altered work capacity. This has been proved on a sample of 63 cases of job injuries and one occupational disease registered in the Occupational safety unit of the Clinical Hospital in Split from May 1994 to May 1995. In all cases the medical doctor of choice, the authorized health insurance board and the authorized insurance company enabled the insured (workers injured at work or having occupational disease, the employer) to make use of their specific insurance rights without waiting for the fulfillment of the prescribed condition of disability, risk of disability and altered work capacity. The authors consider such behaviour to be inadmissible in a state based on the rule of law. If the condition of disability, risk of disability and altered work capacity is unsuitable, as indeed it is, a solution should be sought for in changing the regulations. The simplest way of doing it is to invert the defining and taking over decrees in the Law on Pension and Disability Insurance and the Law on Health Insurance.

[Liability in occupational asbestosis and its harmful sequelae]. / Odgovornost za oboljenje od profesionalne azbestoze i posljedicnu stetu.

A total of 139 cases of occupational asbestosis were registered in companies working with asbestosis in Croatia between the years 1985 and 1994. In the period from 1992 to 1994 thirty-five diseased workers sued in court for compensation of damage. In all suits and at all levels, the employer was judged to be responsible for the damage. Questioning the exclusiveness of responsibility, or at least co-responsibility for the other parties involved in the structure of occupational use of asbestos, the authors ascertained, in all the 35 cases of occupational asbestosis from the sample, that the full responsibility lay with the third party - the State - as representing the unity of the legal, executive and judicious powers.

[Detection of occupational lead poisoning and specific permanent work disability]. / Dokazivanje profesionalnog otrovanja olovom i specificne trajne radne nesposobnosti.

Evaluation of occupational lead poisoning and resultant permanent work disability calls for a procedure which is not easy to conduct. This is because vague, non-manifest lead poisonings and transient pre-poisoning states have lately prevailed over clearly manifested, obvious lead poisonings as were found earlier due to unfavourable working conditions. A reason for this further lies in non-specific clinical symptoms of lead poisoning as well as in lack of a strict set of rules--especially when it comes to assessing biological indicators of abnormal lead absorption in the body--for experts in the disability assessment boards to go by. In view of that the conduct of those taking part in the evaluation procedure (general practitioner of patient's own choice and team of experts in pension and disability assessment boards) is analysed. Many assessments have been found deficient. An amendment to the rules for expert evaluation is proposed.

[The position and role of occupational medicine and specific health care of workers]. / Mjesto i uloga djelatnosti medicine rada i specificne zdravstvene zastite radnika u zastiti zdravlja radnika.

Specific care for workers' health has been largely deficient during the past decade, despite the existing legislation. Consequently, the protection of workers' health has been seriously endangered, with the resultant long-term damage. The main reasons for this were the absence of clearly defined responsibilities regarding the financing and execution of the specific health care measures as well as lack of penalty for their non-implementation. As a result, there was indifference on the part of enterprises, indifference and inadequate organization of occupational health services as executors of the specific health care measures, and indulgence on the part of the court, inspecting services and other competent bodies. The situation could be helped only if a completely different approach, suited to the market economy, were adopted. The State should prescribe only the general rules, while the carrying out of specific health care should, with rare exceptions, be left to the interested parties, enterprises in the first place, and to the law of supply and demand. Naturally, such approach can be successful only in the legal State where the ownership of enterprises and professional services is strictly defined and the court and inspection services are free to act independently. Only then will the responsibility of the owners in respect to the breaking of rules, impairing workers' health and unprofessional work of health and other personnel be raised to an appropriately high level. In such an environment the place and role of occupational health activity as well as its name are bound to see a radical change.

[Work capacity evaluation in inorganic lead exposure]. / Ocjena radne sposobnosti izlozenih anorganskom olovu.

When estimating the work ability of workers exposed to inorganic lead four zones should be differentiated: a zone of normal exposure (I), a zone of abnormal but acceptable exposure (II), a zone of abnormal but still acceptable exposure (III) and a zone of abnormal and unacceptable exposure (IV). In the zone of normal exposure specific work ability is preserved. In zones of abnormal but acceptable exposure specific work ability can, also, be preserved. However, in the zone of abnormal, unacceptable exposure specific work ability, temporarily or permanently, is lost. Combinations of three relevant laboratory tests are presented, which, while warning of the presence, i.e. the effect, of inorganic lead in the organism, directly dictate the estimation of specific work ability (blood lead, ALAD, EP, ZPP). Attention has been drawn to other contraindications, set by positive legislation, which also directly dictate the estimation of workers exposed to inorganic lead. It is emphasized that permanent disruption of relevant laboratory parameters (blood lead, ALAD, EP, ZPP) is a sufficient basis for recognizing occupational lead poisoning, within positive legislation.