A biokinetic model for trivalent or hexavalent chromium in adult humans

Enhanced chromium removal from tannery wastewater through electrocoagulation with iron electrodes: Leveraging the Box-Behnken design for optimization

This study is focused on reducing total chromium level in tannery wastewater through the electrocoagulation process, in order to comply with the maximum permissible limits (MPL) and to determine the effects from its main operating factors. For this purpose, a batch electrocoagulation reactor was manufactured using iron electrodes. Next, the response surface methodology was applied in the experimental design using a Box-Behnken design (BBD) with three factors: current intensity, treatment time, and p H level. In addition, the total chromium removal percentage was taken as a response variable. The corresponding statistical analysis revealed that the treatment time, current intensity, and p H level variables were significant at a confidence level of P - v a l u e < 0.05 . Obtained in this study for a 99 % total chromium removal were: current intensity ( I ) = 2.9 A , time ( t ) = 18.1 min , and p H = 5.6 . Our results indicated that the electrocoagulation process effectively removes total chromium from tannery effluents up to MPL values.

Burden of lung cancer and predicted costs of occupational exposure to hexavalent chromium in the EU - The impact of different occupational exposure limits

BACKGROUND

Exposure to hexavalent chromium [Cr(VI)] occurs widely in occupational settings across the EU and is associated with lung cancer. In 2025, the occupational exposure limit is set to change to 5 μg/m³. Current exposure limits are higher, with 10 μg/m³ as a general limit and 25 μg/m³ for the welding industry. We aimed to assess the current burden of lung cancer caused by occupational exposure to Cr(VI) and to evaluate the impact of the recently established EU regulation by analysing different occupational exposure limits.

METHODS

Data were extracted from the literature, the Global Burden of Disease 2019) study, and Eurostat. We estimated the cases of cancer attributable to workplace exposure to Cr(VI) by combining exposure-effect relationships with exposure data, and calculated related DALYs and health costs in scenarios with different occupational exposure limits.

RESULTS

With current EU regulations, 253 cases (95%UI 250.96-255.71) of lung cancer were estimated to be caused by Cr(VI) in 2019, resulting in 4684 DALYs (95%UI 4683.57-4704.08). In case the welding industry adopted 10 μg/m³, a decrease of 43 cases and 797 DALYs from current values is expected. The predicted application of a 5 μg/m³ limit would cause a decrease of 148 cases and 2746 DALYs. Current costs are estimated to amount to 12.47 million euros/year (95%UI 10.19-453.82), corresponding to 39.97 million euros (95%UI 22.75-70.10) when considering costs per DALY. The limits implemented in 2025 would lead to a decrease of 23.35 million euros when considering DALYs, with benefits of introducing a limit value occurring after many decades. Adopting a 1 μg/m³ limit would lower costs to 1.04 million euros (95%UI 0.85-37.67) and to 3.33 million euros for DALYs (95%UI 1.89-5.84).

DISCUSSION

Assessing different scenarios with different Cr(VI) occupational exposure limits allowed to understand the impact of EU regulatory actions. These findings make a strong case for adapting even stricter exposure limits to protect workers' health and avoid associated costs.

Development of Chromium(III) Selective Potentiometric Sensors for Its Determination in Petroleum Water Samples Using Synthesized Nano Schiff Base Complex as an Ionophore

BACKGROUND

Many analytical techniques, such as X-ray fluorescence spectrometry, inductively coupled plasma atomic emission spectrometry (ICP-AES), and even traditional spectroscopic and fluorimetric methods, are used for the measurement of Cr(III) ions. These methods are sophisticated and very expensive. So, the chipset and the low cost ion selective electrodes were used.

OBJECTIVE

The quantification of Cr(III) ions in various samples of petroleum water using ion selective electrodes was suggested. Nano chromium modified carbon paste sensor (MCPE) and nano chromium modified screen printed sensor (MSPE) based on Schiff base Cr(III) complex are developed.

METHOD

The developed nano Cr(III) Schiff base chelate was characterized utilizing elemental, spectroscopic, and thermal analysis techniques. The proposed nano Cr(III) has a good properties for antibacterial and antifungal activity. The modified carbon paste and screen-printed sensors were fabricated for determination of Cr(III) ion.

RESULT

The proposed MCPE (sensor I) and MSPE (sensor II) obeys Nernstian equation upon incorporating nono Cr(III) ionophore in the paste at 25 °C with a trivalent cationic slope of 18.8 ± 0.2 and 20.0 ± 0.4 mV/decade. They have showed fast response time around 8 and 5 s, and they may be utilized for at least 98 and 240 days without significant changes in MCPE and MSPE potential, respectively. The sensors I and II showed good selectivity for Cr(III) ion toward a wide variety of metal ions or anions as confirmed by potentiometric selectivity coefficients values. The detection and quantification limits were defined alongside the other process validation parameters. The results have been compared well to those obtained by atomic absorption spectrometry (AAS) and the data of F- and t-test indicated no significant difference between the proposed and AAS methods.

CONCLUSION

These sensors have been utilized to determine Cr(III) ions in genuine spiked different petroleum well water samples with satisfactory percentage recoveries, low standard and relative standard deviation values using direct potentiometric and standard addition methods. The proposed method of producing nano Cr(III) complex as a sensor material possesses the distinct advantages of being simple, easily reproducible, appropriate for operation, and highly selective and sensitive.

HIGHLIGHTS

Modified carbon paste and screen-printed electrodes were fabricated based on nano Cr(III) complex as ionophore. The electrodes follow Nernstian behavior and they optimized according to IUPAC recommendation. They showed a high selectivity for Cr(III) ion over many bi or trivalent metal ions and anions. The results obtained compared well with those obtained using atomic absorption spectrometry (AAS). They successfully applied for determination of Cr(III) in petroleum water samples.

Regulations for chromium emissions to the aquatic environment in Europe and elsewhere

Chromium is a controversial element, since it has been classified as essential trace element, to chemically and biologically inert compound, to potent intoxicator. Concerns have been risen for chromium effects on human and aquatic life because chromium has been accused for genotoxicity and carcinogenesis. Metals and their ions or complexes (and thus chromium substances) are included in the indicative list of main pollutants (Annex VIII of the Water Framework Directive (2000/60/EC)). Biological effects of chromium are strongly depended on chromium speciation. No universal Cr^III or Cr^VI discharge limits to the aquatic environment have been suggested by the EU. International bodies within the EU, such as the Helsinki Commission and the Oslo-Paris Convention, have issued recommendations on chromium discharge levels. National Cr^VI and Cr^III discharge limits vary in each EU Member State with respect to the receiving water body (marine water, lake, river, sewer system). The maximum discharge limit to the aquatic environment in EU is 1 and 5 mg L^-1 for Cr^VI and Cr^total, respectively. The present work summarizes EU legislation, with respect to the discharge limits to the aquatic environment for Cr^VI and Cr^III. EU national limits that are currently effective are presented and compared to the limits in other parts of the world, such as Australia, Asia, USA, Latin America and South Africa. It is wise that future perspective of chromium policy should differentiate between Cr^III and Cr^VI discharge limits to the aquatic environment, as analytical techniques become more sensitive and chromium speciation specific, and environmental awareness rises.