Temporal variability in the impacts of particulate matter on crop yields on the North China Plain.

The North China Plain (NCP) is a major agricultural region, producing 45% of China's maize. It is also vital to the Chinese economy, encompassing the Beijing-Tianjin-Hebei megacity region. Anthropogenic factors increasingly impact crop yields on the NCP, and globally. Particulate matter (PM) pollution is a significant problem in this region, where annual average PM concentrations over three times the Chinese national air quality standard were recorded for the Beijing-Tianjin-Hebei megacity region between 2013 and 18. PM absorbs light, reducing total shortwave radiation (SW), thereby limiting plant productivity. However, PM also scatters incoming SW, increasing the diffuse fraction, which has been shown to increase growth and biomass assimilation. The Joint UK Land Environment Simulator (JULES) crop model was used to assess the net impact of these competing changes in light on NCP maize yields. In contrast to some previous analyses, we find that PM-associated decreases in SW outweigh any positive impact on yield from an increasing proportion of diffuse radiation. Furthermore, carbon allocation to different portions of the growing cropchanges during the development cycle. We find significant differences between the effect on final yield of identical changes to diffuse fraction and total SW occurring during different development stages. The greatest simulated yield gains from increased SW and reduced diffuse fraction, consistent with reductions in PM, are observed during the early reproductive stage of development (July-August), when the simulated gain of yield is as much as 12.9% more than in other periods. To further assess the impact of PM-linked changes in SW and diffuse fraction on NCP crop yields, radiation profiles from different city regions were then applied across the NCP. The changes in SW associated with these city regions could increase maize yields across China by ~8 Mt. This would completely offset China's annual maize imports, increasing both national and global food security.

Adjustment of guidelines for exposure of the eye to optical radiation from ocular instruments: statement from a task group of the International Commission on Non-Ionizing Radiation Protection (ICNIRP).

A variety of optical and electro-optical instruments are used for both diagnostic and therapeutic applications to the human eye. These generally expose ocular structures to either coherent or incoherent optical radiation (ultraviolet, visible, or infrared radiation) under unique conditions. We convert both laser and incoherent exposure guidelines derived for normal exposure conditions to the application of ophthalmic sources.

Study of the effect of involuntary user movement on the potential light hazards from some ophthalmic instruments.

A study was undertaken to determine whether involuntary user movement provides a basis for relaxing the measurement conditions for evaluating the potential optical radiation hazards to the eye from slit lamps and indirect ophthalmoscopes. This was accomplished by assessment of the extent to which light from these devices can be maintained in focus on a 1-mm-diameter fiber-optic cable for 45 s. The results suggest that, although involuntary user movements can be significant, they do not provide a basis for relaxing the measurement conditions for evaluating the potential optical radiation hazards to the cornea and lens from slit lamps and indirect ophthalmoscopes.