New study below. Might particularly interest those living in Illinois.
Arsenic occurs naturally in water in some parts of the world. It is found in various forms. It is claimed that the inorganic forms are the most dangerous.
Map of arsenic in groundwater of the United States:
In the Illinois study :
"Illinois Environmental Protection Agency data on arsenic concentrations in drinking water from community water systems throughout the state were linked with county-level prostate cancer incidence data from 2007 to 2011 from the Illinois State Cancer Registry. Incidence rates were indirectly standardized by age to calculate standardized incidence ratios (SIRs) for each county."
"For counties with mean arsenic levels in the second tertile, the SIR was 1.05 ..). For counties with mean arsenic levels in the third tertile, the SIR was 1.10 ... There was a significant linear dose-response relationship observed between mean arsenic levels and prostate cancer incidence".
Other studies that have linked arsenic in water to PCa:
 1989 - Taiwan
 1999 - Utah
 2015 - Turkey
 2015 - Argentina
American Council on Science and Health report (2002) :
"there is clear evidence that chronic exposure to inorganic arsenic at concentrations of at least several hundred micrograms per liter may cause: (1) cancer of skin, bladder, lung (and possibly several other internal organs, including kidney, liver, and prostate)"
Curcumin & arsenic .
"Groundwater arsenic contamination is a global threat to human health and is associated with carcinogenic effects. The biggest cases of groundwater arsenic contamination can be found in Bangladesh and in West Bengal in India. The carcinogenic effects of arsenic are likely mediated through oxidative DNA damage. Therefore, agents with antioxidant capacity may have potential against arsenic-induced genotoxic effects. A field trial from West Bengal evaluated the role of curcumin against the genotoxic effects of arsenic. A total of 286 volunteers exposed to groundwater arsenic were recruited into the study. The participants were randomly assigned to a placebo group (143 persons) and a curcumin-treated group (143 persons). Curcumin was given at a dose of 500 mg twice daily for 3 months in combination with piperine. DNA damage in lymphocytes was assessed by the comet assay and fluorescence-activated DNA unwinding assay. Curcumin was analyzed in blood by high-performance liquid chromatography. Arsenic-induced oxidative stress and curcumin’s antagonistic role were evaluated by measuring reactive oxygen species (ROS) generation, lipid peroxidation, and protein carbonyl contents. The blood samples from this arsenic-exposed population showed severe DNA damage with increased levels of ROS and lipid peroxidation. Three months of curcumin intervention reduced the DNA damage and retarded ROS generation and lipid peroxidation. Curcumin treatment was also associated with significant enhancement in the levels of such anti-oxidants as catalase, superoxide dismutase, glutathione peroxidase, and glutathione. The authors of this study concluded that curcumin may have some protective role against arsenic-induced DNA damage."
Arsenic in food.
Arsenic in rice seems to be unavoidable. "Rice has higher levels of inorganic arsenic than other foods, in part because as rice plants grow, the plant and grain tend to absorb arsenic more readily than other food crops. In April 2016, the FDA proposed an action level, or limit, of 100 parts per billion (ppb) for inorganic arsenic in infant rice cereal." . I think it unfortunate that rice cereal figures so high in infant diets. With a glycemic index of 87, those who eat the stuff several times a day are training to be diabetics IMO. Who knows what the arsenic risk presents to infant prostates?
Gerber switched from sourcing by cost to sourcing by arsenic content & promised to use only rice from California. Gerber also discontinued their "healthier" brown rice products because brown rice has even more arsenic than white.
ConsumerReports video: consumerreports.org/cro/mag...
B] Tea. 
The PCa literature on geen tea is quite persuasive, particularly as it relates to the EGCG content. Green tea consumption is often hypothesized as being one reason that parts of Asia have such low PCa rates. Unfortunately, the leaves of Camellia sinensis can accumulate toxic elements. Considering that some men might consume numerous cups of tea every day, this is of concern.
"Results:. All brewed teas contained lead with 73% of teas brewed for 3 minutes and 83% brewed for 15 minutes having lead levels considered unsafe for consumption during pregnancy and lactation. Aluminum levels were above recommended guidelines in 20% of brewed teas."
"Mercury, lead, arsenic, and cadmium as well as other toxic elements have been found in tea leaves as described in the literature. Lead, arsenic, and cadmium have also been found in brewed black tea. These soil and air contaminants may be directly related to the use of coal fired power plants. The use of coal in China has increased to 3.8 billion tons or about 47% of global coal consumption."
"All brewed tea and tea leaves had detectable arsenic with Chinese oolong teas (organic or regular) having the highest levels. Levels in all teas ranged from 0.06 μgm to 1.12 μgm/L of tea steeped for 3 minutes to 0.08 to 1.27 μgm/L of tea steeped for 15 minutes."
"Brewed tea appears to contain numerous toxic elements such as arsenic and cadmium. However, none of these toxicant levels were above present day acceptable standards."
"Despite smaller amounts of cadmium and arsenic there is concern for long-term bioaccumulation."
C] Dietary lipids - inverse risk! 
"Of the 20 dietary factors inversely associated with ln-transformed toenail arsenic, 16 were dietary lipids ..."
D] Fatty fish. 
"In contrast to the relationships with other dietary lipids, we found that intake of long chain n-3 polyunsaturated fatty acids, both individually and combined, were positively associated with toenail arsenic concentrations ..."
E] Alcohol (Rats!). 
"Consistent with previous epidemiological and modeling studies, we found strong positive associations between toenail arsenic concentrations and consumption of ethanol ..."
F] Brussels spouts. 
"Of all the diet items evaluated, only beer, white wine, and Brussels spouts were statistically significant after correction for multiple testing ..."
"Increased consumption of Brussels sprouts was also positively related to toenail arsenic: the models predict a 10% increase in toenail arsenic when consumption increases from never eating Brussels sprouts (5th percentile consumers) to eating them once per week (95th percentile consumers"
"This finding is consistent with recent studies documenting high concentrations of arsenic in Brussels sprouts and other cruciferous vegetables that may result from their high concentrations of sulfur; arsenite is known to bind preferentially to sulfur-containing compounds as part of cellular detoxification of arsenic in plants."