Excess caesium can lead to hypokalemia, arrythmia, and acute cardiac arrest, but such amounts would not ordinarily be encountered in natural sources.
ɛksˈɛs sˈiːsiəm kæn lˈiːd tə hˌaɪpoʊkeɪlˈiːmiə, ɚɹˈɪθmiə, ænd ɐkjˈuːt kˈɑːɹdiˌæk ɚɹˈɛst, bˌʌt sˈʌtʃ ɐmˈaʊnts wʊd nˌɑːt ˌɔːɹdɪnˈɛɹᵻli biː ɛŋkˈaʊntɚd ɪn nˈætʃɚɹəl sˈoːɹsᵻz.